Circles

10.

Following the diagram, there is a theorem that states:

AX * BX = DX * EX

You can use that to solve for x. 

$(x+10)(x+1)=x(x+13)\\ x^2+11x+10=x^2+13x\\ 2x=10\\ x=5$

I am not going to answer 5 and 9, but just tell you how to do it. 

You use that formula to solve for x and find pq. Good luck!

I hope this helped,

Gavin