n^2 - 2n/n^2 - 7n=?

(n^{2}-2n)/(n^{2}-7n) = ? Notice that n can be factored out of the numerator & denominator

The problem becomes [n(n-2)]/[n(n-7)] and you can cancel the n's since they are factors (multiplying) and the final answer is (n-2)/(n-7)