Question

Find the measure of angle R in parallelogram PQRS
Angle Q= 3y-78
Angle P= 3y

Answer 1

∠ R = 129°

Explanation:

In a parallelogram

• consecutive angles are supplementary ( sum to 180° ), that is

• opposite angles are congruent ( equal )

∠ P + ∠ Q = 180 ( substitute values )

3y + 3y - 78 = 180 ( simplify left side )

6y - 78 = 180 ( add 78 to both sides )

6y = 258 ( divide both sides by 6 )

y = 43

Then ∠ P = 3y = 3 × 43 = 129° , so

∠ R = ∠ P = 129°