I believe the answer is fairly straightforward but fear it can not be that simple.
The problem i want to solve involves multiple variables, lets call them A,B,X,Y. Each of these variables represents a value between 1 and 100. They each have a percentage influence on a total, T, that is also a value between 1 and 100. T is unknown, and A,B,X,Y are known. the specific values arent important. Am i correct to assume that the equation is as simple as multiplying each variable by its percentage of influence then adding these together?
So for example 10%(A) + 25%(B) + 35%(X) + 30%(Y) = T
You have reinvented the idea of a weighted average. It's probably the right solution to your problem. I can't be sure without knowing something about the meanings of the variables.
See https://en.wikipedia.org/wiki/Weighted_arithmetic_mean