So,
First you have to distribute the numbers outside of the parentheses (you multiply them with the numbers inside of the parentheses
-18+(-9a) + 8a +36=11
Then collect like terms
18-1a =11
-18 -18
---------------------
-1a=-7
Divide both sides by -1
a=7
The answer is 80, 2x+3x+4x=180, so x=20. 20*4=80.