Me i'm desperate!

solve v=(1/3)(pi)h^2(3r-h) for r.

(if you want to see the question better, look at the picture)

also, explain how to solve it. (and if you could provide a visual, that would be great.)

The marked price of an article is 25% above its selling price and the cost price is 30% less than its marked price . find the discount percent and gain percent. only a brainlest can solve it i will mark you brainlest