Given the system of equations \begin{cases} x(x+y) &=& 9 \\ y(x+y) &=& 16 \end{cases}
the value of xy can be written as \frac{a}{b} where a and b are positive coprime integers. Find a+b.
the value of xy can be written as \frac{a}{b} where a and b are positive coprime integers. Find a+b.