Can someone help me solve this expression:
15-20×-5+–1=

- anonymous

Can someone help me solve this expression:
15-20×-5+–1=

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- katieb

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- anonymous

Hey again :D one sec.

- ccswims

remember PEMDAS

- anonymous

Uh -9-20x, but if you are distributing then -9=20x = -2.222222222

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## More answers

- ccswims

OH WAIT. lol i thought that "x" was a multiply symbol XD

- mathstudent55

Is this the expression?
\(\Large 15 - 20 \times (-5) + (–1) = \)

- anonymous

Yeah

- anonymous

here is the math :P
15-20x-5+-1
15-5+-1=-9
-9-20x=
+20x to both sides = -9=20x
simple division leads us to -2.222222

- anonymous

Wait no there aren't any parenthesis

- mathstudent55

You must follow the correct order of operations.
Multiplications and divisions come before additions and subtractions.

- anonymous

simple isolation of the variable right ?

- anonymous

Yeah @Etrainx

- calculusxy

\[15 - 20 \times (-5) + (-1)\]
\[15 + 100 + (-1)\]
\[115 + (-1)\]
\[114\]

- anonymous

Should I multiply -20×-5 since its multiplication & following the order of pemdas ?

- anonymous

OH i see

- anonymous

you have 20 * (-5)

- anonymous

i have 20x

- anonymous

But the 20 is negative

- calculusxy

The x really means multiplying. You're not working with variables, I believe.

- calculusxy

@Halia You're correct. It's -20 because of the minus sign.

- anonymous

when you subtract a negative number it becomes positive though.

- anonymous

Yeah @calculusxy

- calculusxy

@Etrainx You need to work with PEMDAS and this states that multiplying is before subtracting. Thus, you need to do -20 times -5.

- anonymous

Wait so I multiped -20×-5 and I got +100

- anonymous

I think these mathletes have it from here :P

- calculusxy

Yes that's correct .

- mathstudent55

That means you must start with \(20 \times (-5)\)
\(\Large 15 - \color{red}{20 \times (-5)} + (–1) =\)
\(\Large = 15 - \color{red}{(-100)} + (–1) \)
Now we only have additions an subtractions, so we do them in the order they appear from left to right:
\(\Large =15 - (-100) + (–1) \)
\(\Large =15 + 100 -1 \)
\(\Large =115 - 1\)
\(\Large =114\)

- calculusxy

The work that I did but explained in a better way @mathstudent55

- calculusxy

;)

- calculusxy

It's confusing, but just remember to take into consideration the sign (plus or minus) because that determines whether the following integer will be negative or positive.

- anonymous

Mkay I understand it now :) thanks guys I really appreciate it !!!

- calculusxy

You're very welcome @Halia :)

- mathstudent55

Order of operations PEMDAS
P - first do what is inside parentheses
E - then do exponents
MD - then do multiplications and divisions from left to right in the order they appear
AS - finally do additions and subtractions in the order they appear from left to right

- mathstudent55

You're welcome.

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