X^2 + x-12 = 0 if a is a solution of the equation above and a> 0, what is the value of a?

X² + x - 12 factors into (x + 4) and (x - 3)

So if you set each factor equal to zero you get the following solutions

(x + 4) = 0 ⇒ x = - 4 which cannot be "a" since a > 0 and - 4 is not > 0

(x - 3) = 0 ⇒ x = 3 this is the value of "a"

answer: a = 3