a: 70
b: 57
c: 53
C is equal to 53 because they are both alternate interior angles.
All triangles must add up to 180, so by subtracting the known angles from 180, you can get the missing angle:
180-70-53=57
The final angle on the left triangle is 57, therefore B would be 57 because they are alternate interior angles.
You subtract 57 and 53 from 180 to get angle A, which would be 70.