Isolating Variables with exponents

[fisselt]

I've done a few searches but cant really find a proper answer for my question. I'm having issues with isolating variables for some reason and need a way to check my work. I am able to do this with my 89 until I have an equation where I need to solve for a variable with an exponent.

Doing something basic like the volume of a sphere:

solve(v=(4/3)πr^3,r^3)

I get "argument must be a variable name"

If I only want to solve for "r" it works wonderfully.

Thanks for the help.