Whoa, Jackieboy. If you have 3 variables, you need 3 equations to solve for them uniquely. As it is, all we have is one: That they sum to A. Even if we fix X at 25, for example, for any given value of A (say, 100), then all we know is that Y + Z = 75. That's not much help, since any value of Y is possible, as long as Z becomes 75 - Y. That means we can have any value of Y, and Z is determined. So the value of Y varies freely. And remember that in the first step we fixed X at 25; who says that's the value? It can also float freely. So the answer is that you actually cannot answer the question until there are 3 equations, if there are 3 variables.