Question 172341
if 3x=6x-15 
then 
Solving for 'x':
3x=6x-15
adding 15 to both sides:
3x+15=6x
subtracting 3x from both sides:
15 = 3x
dividing both sides by 3:
5 = x
.
Now, we plug our value of 'x' into:
x+8
= 5+8
= 13  (this is what they're looking for)