This is called a literal equation, or an equation with multiple variables. You solve it the same as you solve any other equation, but the variables stay there the whole time.
If they want "r" to be the subject, then they want you to solve for r. This means that you need to get the variable r by itself on one side of the equation, but still have the equation be equivalent to it original form.
I'm going to show you, in steps, how to solve this problem:
<span>V=πr²h
Divide both sides by "</span>π²h<span>" </span>V/π²h=(πr²h)/<span>π²h </span> V/(π²h)=r
