Question

p = 2q+3

p+q = 9

Answer 1

You have 2 equations and 2 unknowns. You can solve by many methods, lets try substitution method.

p=2q+3 <-- eqn 1

p+q = 9 <-- eqn 2

plug eqn 1 into eqn 2:

2q + 3 + q = 9

simplify:

3q=6

q=6/3 = 2

Now you have q=2 , you can plug that value into eqn 1 or 2 to find the value of p