First add both together and equal them to 180 because that is a supplementary angle.
3q + 15q + 18 = 180
Simplify
18q + 18 = 180
Subtract 18 from both sides
18q = 162
Divide by 18
q = 9
Plug 9 in for q in the equation “15q + 18”
Then your answer should be 144.