Finding the third side of a triangle given the area

Perimeter =$\frac{(a+b+c)}{2}$

Area = $A=\sqrt{p(p-a)(p-b)(p-c)}$

How do I simplify the above two equations to solve for c?

Perimeter =$\frac{(a+b+c)}{2}$

Area = $A=\sqrt{p(p-a)(p-b)(p-c)}$

How do I simplify the above two equations to solve for c?