A: angle 3 is 103. You add up the angles given, and subtract it from 180, since triangles equal/add up to 180.
so 52+25=77.
180-77=103.
B: Since angle 3 and 4 are on the same line, they're supplementary, so they add up to 180.
180-103=77.
Angle 4 is 77.
