To solve for y, you do not get a value as there are no values in the equation. You can however still solve, as long as you make the equation "y =". To do this, you need to get y by itself, and we can see that it is being multiplied by r. To move the r onto the other side, we therefore have to divide by r on both sides. This leaves us with y = Z/r, which is your answer.
I hope this helps!