(36 + xy) / (uw) = z
If I follow what you're saying, each side of the equation is multiplied by 3
(giving value 3z to right side), but only the x is affected on the left side.
So we'll let x's new value = k:
(36 + ky) / (uw) = 3z
36 + ky = 3uwz
ky = 3uwz - 36
k = (3uwz - 36) / y
So the value of x needs to be changed to the equivalent of (3uwz - 36) / y
Best I can do for you; 1st time I see such a problem.