The square of mark's age 3 years ago is 6 times the age he will be in 9 years. what is his age now? 9 12 15

This is how you do it!

(x-3) ^2=6 (x+9)

x^2 - 6x + 9 = 6x + 54

x^2 - 12x + 9 = 54

x^2 - 12x - 45 = 0

Then Factor the left side

(x + 3) (x - 15) = 0

x + 3 = 0 and x - 15 = 0

x = - 3 and x = 15

The only option that can be an age is 15

Therefore the answer is 15