For this one, I’m going to assume that you’re talking about multiple regression. In doing multiple regression, it is possible to have a number of x’s in the model. The regression simply states the model is significant, it cannot tell how each variable contributes individually (because of potential interaction). To clearly know how much a single variable contributes, you would have to do additional experimentation. However, with good process knowledge, this “separation” of variables is often not required. I hope that helps!