In the quadrilateral, one pair of sides are parallel and the other pair are congruent. Therefore, this is an isosceles trapezoid. Recall that in an isosceles trapezoid, leg angles are supplementary. This means the sum of m∠ R and m∠ Q equals 180^(∘).
m∠ Q + m∠ R =180^(∘)
By substituting m∠ R with its measure in this equation, we can solve for m∠ Q by performing inverse operations.