Because RPS is 120 degrees and it is bisected by PQ (cut into 2 equal parts), we can determine that both sides are 60 degrees. Set the expression 5p+30 equal to 60 to find the value of p.
5p + 30 = 60
5p = 30
p = 6
So now you have determined that p = 6, and the measure of RPQ is 60 degrees.