Finding Percentage Contribution of a Variable in an Equation

Question

I have an equation, for example:

$$ y=a-b+c $$ I am actually confused how exactly to find the contribution of the variables individually to the entire equation. Due to the negative sign, following $\frac a{a-b+c}$ sometimes gives percentage higher than 100%, which kinda violates the rule. Is there a better or a more appropriate method to find the individual contribution?

Thanks in advance

Answer 1

What rule are you talking about? Assuming $a,b,c,y$ are all positive, it can be that $a \gt y$, so $\frac ay \gt 100\%$ The contribution from $b$ will be negative and the contributions of the three will add to $100\%$