## anonymous one year ago Can someone help me solve this expression: 15-20×-5+–1=

1. anonymous

Hey again :D one sec.

remember PEMDAS

3. anonymous

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

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

5. mathstudent55

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

6. anonymous

Yeah

7. 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

8. anonymous

Wait no there aren't any parenthesis

9. mathstudent55

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

10. anonymous

simple isolation of the variable right ?

11. anonymous

Yeah @Etrainx

12. calculusxy

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

13. anonymous

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

14. anonymous

OH i see

15. anonymous

you have 20 * (-5)

16. anonymous

i have 20x

17. anonymous

But the 20 is negative

18. calculusxy

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

19. calculusxy

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

20. anonymous

when you subtract a negative number it becomes positive though.

21. anonymous

Yeah @calculusxy

22. calculusxy

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

23. anonymous

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

24. anonymous

I think these mathletes have it from here :P

25. calculusxy

Yes that's correct .

26. 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: $$\Large =15 - (-100) + (–1)$$ $$\Large =15 + 100 -1$$ $$\Large =115 - 1$$ $$\Large =114$$

27. calculusxy

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

28. calculusxy

;)

29. 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.

30. anonymous

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

31. calculusxy

You're very welcome @Halia :)

32. 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

33. mathstudent55

You're welcome.