A_{m,n} = \frac{12m + n - 3mn +7}{5m - 2n - 2mn + 5} = \frac{\left(5m-2mn\right)+\left(7m+7\right)-\left(n+mn\right) + \left(2n-5\right) + 5}{\left(m+1\right)\left(5-2n\right)}=