In this case we must apply the properties of supplementary angles and opposite angles.
1 .
opposite angles
∠ 1 = 120 °
supplementary angles
∠ 1 + ∠ 2 = 180
120 + ∠ 2 = 180
∠ 2 = 180 - 120
∠ 2 = 60 °
The same properties can be applied in the other exercises to solve them.
The solution is:
∠ 1 = 120 °
∠ 2 = 60 °
