Question

how do you solve 2e - 12 = 7e + 8? i got 4 but the answer key says it's -4. what do you subtract from both sides?

Answer 1

First you subtract -2e from both side

Answer 2

2e - 12 = 7e + 8. We need to solve for e.
First, subtract 7e from each side to get the variables on a side and the numbers on the other:
2e - 12 = 7e + 8
2e - 12 - 7e = 7e + 8 - 7e
-5e - 12 = 8
We need too to add 12:
-5e - 12 + 12 = 8 + 12
-5e = 20
Now you divide each side by -5 so you can get the variable e alone on the first side, and its value on the other:
(-5e)/-5 = 20/-5
e = -4 (20/-5 = -4; Do not forget that when dividing a positive number by a negative number, the result is strictly negative!!)

You can recheck your answer (very important):
2e - 12 = 2*(-4) - 12 = -8-12 = -20
7e + 8 = 7(-4) + 8 = -28 + 8 = -20
So 2e - 12 = 7e + 8 = -20
The answer has been approved.

Hope this Helps! :)