To isolate the variable you need to remove the terms from the side with the variable to remove the terms you need to do the same thing on both sides.
-2/3n + 7 = 15
First step is to subtract 7 from both sides to get:
-2/3n = 8
Now divide both sides by -2/3 to get:
N = 8 / -2/3
Then to solve for n simplify to get:
N = -12