Question 501662
If PQ and QR are perpendicular, they will add to 90 degrees.
4 + 7a + 9 + 4a  = 90
13 + 11a = 90
11a = 77
a = 7
Angle PQS = 53
Angle SQR = 37
53 degrees + 37 degrees = 90 degrees.
This does check.
Cleomenius.