13x=7x+5

- anonymous

13x=7x+5

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- PhoenixFire

Solve for x?

- anonymous

yes, i dont even know where to start!!!!

- zzr0ck3r

subtract 7x from both sides and tell me what you got

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## More answers

- anonymous

5/6

- anonymous

=x

- zzr0ck3r

@rainbow dont just give answers. Please read rules.

- PhoenixFire

\[13x=7x+5\]
Subtract 7x from both sides.
\[13x-7x=7x-7x+5\]
Combine like terms
\[6x=5\]
Divide both sides by 6
\[x={5 \over 6}\]

- zzr0ck3r

we are not saposed to give them the answers, you should involve them in getting the answer...

- PhoenixFire

Sorry @zzr0ck3r I'll remember for next time.

- anonymous

AHHHHH..Thank you so much Phoenixfire for explaining!!!

- anonymous

X-2/5=1/2

- anonymous

how would i start this one?

- PhoenixFire

Add 2/5 to both sides. What do you get?

- anonymous

im horrible at this!!! add 2/5 to 2/5 and 1/2?

- PhoenixFire

Yes. type out the entire equation with 2/5 added to both sides.

- PhoenixFire

@mlbach Did you get it?

- anonymous

no, im sorry, trying to do it on paper

- anonymous

im 38 and math is like a foreign language to me!

- PhoenixFire

You have \[x-{2 \over 5}={1 \over 2}\]
So, add 2/5. You get:
\[x-{2 \over 5}+{2 \over 5}={1 \over 2}+{2 \over 5}\]
Try solve from there.

- anonymous

x-4/5=9/10

- anonymous

is that right...9/10

- PhoenixFire

You can see that the -2/5+2/5 results in 0.
\[x-0={1 \over 2}+{2 \over 5}\]
But you got the right hand side correct.

- anonymous

ok, they cancel each other out right?

- PhoenixFire

Correct!
So, \[x={9 \over 10}\]

- anonymous

YAY!!!!! thank you!!!

- PhoenixFire

No problem. :)
Any other problems?

- anonymous

2/7X=6

- PhoenixFire

\[{2 \over 7}x=6\]
Divide both sides by 2/7. The one the left will cancel and then you're left with x=??

- anonymous

how do i know that im dividing?

- PhoenixFire

\[{2 \over 7}x=6\]
Divide by 2/7\[{{{2 \over 7}x} \over {2 \over 7}}={6 \over {2 \over 7}}\]

- PhoenixFire

\[{{2 \over 7} \over {2 \over 7}}=1\] Do you understand that?
Anything divided by itself is 1.

- anonymous

yes

- anonymous

i just dont know how to do 6 divided by 2/7

- PhoenixFire

So, that leave \[1x={6 \over {2 \over 7}}\]
Now, a trick is to dividing by fractions:
\[{a \over {b \over c}}={{c \over b}a}\]
You flip the bottom fraction and multiply the top by it.
Giving you: \[{6 \over {2 \over 7}}={7 \over 2}6\]
Or \[{7*6} \over 2\]

- PhoenixFire

Sorry about the bad grammar.. That was truly horrible.

- anonymous

21?

- PhoenixFire

Yes!
\[x=21\]

- anonymous

can i just put you in my pocket and and take you to class with me?

- PhoenixFire

Hahaha. Yes, if you have a cell phone and internet on it. :)

- anonymous

lol

- anonymous

A telephone book has white pages and yellow pages. ¾ of the book consists of the white pages; the yellow pages number 300. What is the total number of pages in the telephone book?

- anonymous

how would i start this one

- PhoenixFire

White=3/4 of the book
Yellow=1/4 of the book.
So, if 1/4 of the book is 300. How many total pages are there?

- anonymous

900

- PhoenixFire

Almost.
Y=yellow=1/4=300
W=white=3/4=300*3
T=total=W+Y=(300*3)+300=1200

- anonymous

ah. i got it

- anonymous

A theater usher at a Broadway musical finds that ½ of the patrons attending a performance are in their seats by show time. The remaining 60 people are seated after the opening number. If the show is always a complete sellout, how many seats does the theater have?

- PhoenixFire

This one is mostly a play on words.
If you single out a few words: "1/2", "remaining", "sellout"
From this you can see that "sellout" says all seats are taken.
"remaining" means those not seated initially.
"1/2" the initial people seated.
So, if "half" of the attendees are seated before the show, and the "remaining" are seated after the first number. How many seats are there in the theater which is "sold out (ie all seats taken)"?

- PhoenixFire

*** "remaining 60" ***

- anonymous

120?

- PhoenixFire

Correct!

- anonymous

YAY!!!! lol

- PhoenixFire

Getting the hang of it?

- anonymous

right now i am, but come test time, I'll draw a blank!

- anonymous

Of those invited to a wedding, 2/7 were friends of the bride. The friends of the groom numbered 65. How many people were invited to the wedding

- PhoenixFire

Haha. Of course. Nobody can avoid the blank come test time.

- anonymous

unfortunatley not!

- anonymous

what do i look at first?

- PhoenixFire

bride=2/7
Therefore, groom=5/7=65
You can take this known number as a percentile of the total attendees.
\[{5 \over 7}T=65\] Where T= the total number of people attending.
Now solve for T.

- anonymous

where did you get 5/7 from?

- PhoenixFire

Well if the brides guests are 2/7 of the attending people. then the grooms is the remaining guests. Correct? so 1-2/7 = 5/7

- anonymous

oh ok

- PhoenixFire

To solve for T you use the same method as one of the other problems above. The funny trick with dividing by fractions.

- PhoenixFire

Got it yet?

- anonymous

not quite

- PhoenixFire

What are you stuck on?

- anonymous

5/7T=65....i get stuck on how to work the problem out

- PhoenixFire

Well you want to isolate T. Because that's the unknown variable that you want to become known.
So in this case, the only way to do that is to remove the 5/7 from T.
You will want to divide by 5/7 to make it cancel out, leaving T alone on the left.

- anonymous

so do i divide both sidesby 5/7?

- anonymous

answer is 91?

- PhoenixFire

Yes. Because if you change the equation on the left, you have to change it in the same way on the right for the equality to hold.
91 is correct!

- anonymous

awesome!!!!

- anonymous

thank you so much for your help, I appreciate it!

- PhoenixFire

No problem at all. Become a fan of me, and if you need help just send me a message.

- anonymous

Done!

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