Algebra
posted by Jack Reeg .
Rays PQ and QR are perpendicular. Point S lies in the interior of angle PQR. If angle PQS= 4+7a and angle SQR=9+4a, fing angle PQS and angle SQR.

Angle PQR is 90 degrees.
4+7a + 9+4a = 90
Solve for a, and substitute back into the expressions for the angles