Considering the lines e, f, and a, angles (x + 1)° and (x - 3)° are same side exterior angles, then they are supplementary, that is,
(x + 1) + (x - 3) = 180
(x + x) + (1 - 3) = 180
2x - 2 = 180
2x = 180 + 2
x = 182/2
x = 91
Considering the lines a, b, and e, angles (x + 1)° and y° are alternate side interior angles. Therefore, they are congruent, that is,
x + 1 = y
Substituting with the value of x:
91 + 1 = y
92° = y
