It's not clear whether it should be 18 - 7x or 7x - 18, it listed 18 first so that's how I tried it.
1 + (18 - 7x) = -9
subtract 1 from both sides:
18 - 7x = -10
subtract 18 from both sides:
-7x = -28
divide both sides by -7:
x = -28/-7 = 4
I should have explained each step when I first wrote my answer. Sorry.