Question

What am I supposed to do?

Answer 1

2x+8+x=15

combine like terms [ 2x + x = 3x]

3x+8=15

subtract 8 from both sides [ 8-8 = 0 , 15-8 = 7 ]

3x=7

divide both sides by 3 [ 3x/3=7/3]

X = 7/3

Answer 2

First you combine like terms on the same side so 2x + 8 + x would become 
3x + 8.
Now the equation is 3x + 8 = 15.
You subract 8 from both sides so it is then 3x = 7.
Finally divide 3 from both sides.
The answer is x = 7/3