Question

Work out the size of angle y.

Answer 1

y = 38°

Explanation:

y + 91° = 129° (opp. ∠s = ext. ∠)

y = 129° - 91°

y = 38°

In a triangle, the two opposite angles of an angle equals to the exterior angle that is adjacent to that angle on a straight line.

Answer 2

y = 38

Explanation:

exterior angle of a triangle = sum of its interior opposite angles

129 = 91 + y

y = 129 - 91

y = 38