Differentiating the Integral Form of the Continuity Equation for Fluids

Homework Statement

I am working on a problem that asks to use the integral form of the continuity equation (for a steady flow) and show that it can equal this (by taking the derivative of it): dr/r + dV/V + dA/A = 0 where V is Velocity and r is the density.

Homework Equations

What would the derivative be with respect to?

The Attempt at a Solution

I was able to bring it down to: rVA=0 but I am unaware how to differentiate this so that it looks like the equation above.

Thanks.