h = v/lw
Basically, in order to solve for h, you have to get h by itself. The way you would do that is divide lwh by lw in order to leave h by itself.
v = lwh/lw
But what you do to one side of the equation, you have to do to another, so you would also divide v by lw.
v/lw =lwh/lw
v/lw = h