Answer:
∠ A = 130° , ∠ B = 50°
Step-by-step explanation:
supplementary angles sum to 180°
express ∠ A in terms of ∠ B , that is ∠ A = 3∠B - 20 , then
∠ A + ∠ B = 180° , that is
3∠B - 20+ ∠B = 180 ( add 20 to both sides )
4∠B = 200 (divide both sides by 4 )
∠ B = 50°
∠ A = 3 × 50° - 20 = 150° - 20° = 130°
