Question 604796
girl's age in present = x

{{{x + 12 = x^2}}}
{{{0 = x^2 - x - 12}}}
0 = (x - 4)*(x + 3)
x - 4 = 0 or x + 3 = 0
x = 4 or x = -3
since the age can't be a negative number, we choose x = 4


so, at the present, the girl is 4 years old