Question

A and B are supplementary. A is 20 less than three times the measure of B. What are the measures of A and B?

Answer 1

∠ A = 130° , ∠ B = 50°

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°