Answer:
x = -1
Step-by-step explanation:
combine like terms on both sides (like terms refers to the variable, x in this case) so
3x + 7 = 11x + 15
then get x terms to one side and non-x terms to the other
this gives you: 7 - 15 = 11x - 3x
-8 = 8x
dived both sides by 8 (since its the constant with x) which gives you
x = -1
hope I could help ( I messed up at first but I fixed it)