What must m∠QPS be for PQRS to be a parallelogram?
There is a quadrilateral PQRS in which the length of side PQ is 6b, the length of side QR is 4a+1, the length of side RS is 11b-10, and the length of side PS is 2a+9. The measure of angle PQR is (6x+13) degrees and the measure of angle PSR is (7x-5) degrees.