It will be c- 20:
4q and 2(q+30) have to equal the same therefore q=30 which makes both these equations equal.
3p + 4q then have to equal 180 as they are on a straight line so you know q=30 so 4x30=120 so 180-120=60
Then 60/3=20 and that is your answer.
Hope this helps :)
