Constructing a Quadratic equation.

The question requires me to construct an equation and solve for y.

Q. When a mother's age is then the daughter's age is y. When the mother lives to the age of 13y then the daughter will be the same age of

Find the age of the daughter?

Ok here goes:

The mothers age >

Now solve using quadratic formula a=1, b=26, c=168

[tex] \frac{-26}{2} + - \frac{\sqrt{676-672}{2} [\MATH]

[tex] -13 + - \frac{\sqrt{4}{2} > x= -12 or x=-14 ?

[\MATH]

So, daughter's age is 12 or 14? But that doesn't make sense because if the daughter's age at the start was 12, then mother's age would be 144! Not feasible..(Thinking)