Answer:
c = s (s-P)
Step-by-step explanation:
To solve the expression for c, we have to do different operations in order to leave c on one side and the rest of the variables on the other.
First we have:

The next step would make the minimum common multiple for the denominator:
Now we're going to cross multiply:

Now we're going to move the s² to the other side:

We have -c instead of c, so we're going to change the signs of all terms:

Now we solved for c but we can still make one more step because both terms on the left side have an s.

Thus c = s (s-P)