Answer:
∠ a = 30° , ∠ b = 90°
Explanation:
∠ a and 150° are a linear pair and sum to 180° , that is
∠ a + 150° = 180° ( subtract 150° from both sides )
∠ a = 30°
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the sum of the 3 angles in a triangle = 180° , that is
∠ b + ∠ a + 60° = 180°
∠ b + 30° + 60° = 180°
∠ b + 90° = 180° ( subtract 90° from both sides )
∠ b = 90°