157 is an exterior angle to A.
157+ A = 180
A = 180-157
A = 23°
C and 42° both add up to 180°
C+42 = 180
C = 180-42
C= 138°
C and B(exterior) are corresponding angles: (C=B)
138+ B (int)= 180
B= 180-138
B= 42
The sum of all interior angles of a triangle adds up to 180°.
23+42+ F = 180
F= 180-42-23
F = 115
