Whenever you're solving for a variable, you want to isolate the variable, or get it by itself. start by subtracting z from both sides:
u=vw+z
-z -z
u-z=vw
Then, divide both sides by w
u-z=vw
/w /w
Leaving you with (u-z)/ w = v
(the u-z doesn't need to be in parenthesis, I'm using it to demonstrate that the expression u-z is being divided by w, instead of just one.