Question: a x a - b x b = 9, and a - b = 1. What is the value of a + b ?

Question: a x a - b x b = 9, and a - b = 1. What is the value of a + b ?
Hint: a x a - b x b = a x a - b x b + a x b - a x b. Do you know the distributive property of multiplication over addition ?