Because vertical angles always equal each other. linear pairs always equals 180 degrees always. hope this helps :)
The answer is B.
(the equation to solve this with is: a^2 + b^2 = c^2)
For this, we will be using the quadratic formula, which is
, with a=x^2 coefficient, b=x coefficient, and c = constant. Our equation will look like this: 
Firstly, solve the multiplications and the exponents: 
Next, do the addition: 
Next, your equation will be split into two:
. Solve them separately, and your answer will be
The value of p would be 40. This is because the ratio of p:q = 10:5. this could be simplify into p:q = 2:1. Applying the ratio p:20 = 2:1, P=40.