Answer:
4
Step-by-step explanation:
Let x represent her present age. The given relation is ...
x +12 = x^2
Putting this in standard form, we can factor it:
x^2 -x -12 = 0
(x -4)(x +3) = 0
Solutions to this quadratic are x = 4, x = -3. The -3 solution is extraneous in this context.
The girl's present age is 4.
