A hard-working analysis would have read the big red instructions at the top of the forum first:
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Please always present any of your own work with a post so that someone can see where you're at and guide you from there.
But a hint. ANY time you have a problem like this involving equations, write down all of your equations first. Then start plotting in what you have, and work your way towards what you don't have. Sometimes one has to be solved to use that answer in another one to solve it. Using your extended equation for ROI, you can get profit margin and sales very quickly. Then go from there.