Because line PQ and line PR are both tangent to circle S, it would result in them being equal. So first to find PQ, you would have to find the value of variable x. To do this you would set both equations equal to each other and solve
6x - 9 = 2x + 3
-2x -2x
4x - 9 = 3
+9 +9
4x = 12
x = 3
Now you have to substitute 3 back into the equation for PQ:
6(3) - 9
18 - 9
= 9
Resulting in PQ = 9, to check your answer, take the value of x (3) and substitute it into PR and you should also get 9
