These problems are rather easy. What you need to remember is that the parallel line segments will always contain the same number so the angle (65) on b2 would be the same angle for a2, bt at. so now to find the angle for b1 and a1 so we would subtract 65( the angle for B2) by 180 (the angle for a line) which would come out to be 115.
i hope this helped you, if not heres a link to a website that explains what i tried to explain.
