Solve for k. i tried many times to get it right but i still get stuck when i am close to finding the m=1/k+n

The denominator is k, according to user who posted the question.

We need to solve for k.

In order to solve for k, we need to isolate k, meaning
1. subtract n on both sides in order to isolate k, simplify



2. multiply k on both sides, do not forget the parentheses,

3. divide by (m-n)   (do not forget the parentheses), simplify



So the final answer is
k=1/(m-n)     do not forget the parentheses.

1195 was the store owner's profit.