.
Using obvious notations, we have these two equations
L = P + 5 (1) ("Leo is 5 years older than Pat.")
L + 10 = 2P (2) ("In 10 years, Leo will be twice Pat's present age.")
From equation (1), express P = L - 5. In equation (2), replace P by L-5, based on it. You will get
L + 10 = 2*(L-5).
Solve for L :
L + 10 = 2L - 10
10 + 10 = 2L - L
====================> 20 = L.
ANSWER. Leo is 20 years old now.
Solved.
