Question

angle A and Angle B are supplementary angles. if the measure of angle B is 20 less than 3 times the measure of angle A, find the measurement of angle B.

Answer 1

∠ B = 130°

Explanation:

given ∠ B = 3 ∠ A - 20

supplementary angles sum to 180°

sum A and B and equate to 180

∠ A + 3 ∠ A - 20 = 180

4 ∠ A - 20 = 180 ( add 20 to both sides )

4 ∠ A = 200 ( divide both sides by 4 )

∠ A = 50

that is ∠ A = 50° and

∠ B = 3 ∠ A - 20 = 3 × 50 - 20 = 150 - 20 = 130°