Please explain how this ratio is being calculated A,B and C are partners of a company. A receives $\frac{x}{y}$ of profit. B and C share the remaining profit equally among them.
A's income increases by $I_a$ if overall profit increases from P% to Q%. How much A had invested in their company.
I know the answer: $\frac{I_a\cdot100}{P-Q}$.
This may be a very simple question, but I don't understand how it comes.

When you say profit increases from $P\%$ to $Q\%$ do you mean something different from $\frac P{100}$ to $\frac Q{100}$ (of what-sales, for example-are you assuming that sales stay the same)?  If not, A receives $\frac xy \frac Q{100}$ instead of $\frac xy \frac P{100}$.  You have a problem of units-$\frac xy \frac Q{100}$ is unitless, but you pay A dollars.
