Can someone help me with this?

Interpret the following expression (5y^2-7)^3/(2y)^2

Robin spent 25% more time on his research project than he had planned he’s been an extra h ours on the project which of the following expressions could represent the number of hours rob actually spent on the project

If it 8 inch candle burns at 7/10 inch per hour and a 6 inch candle burns at 1/5 inch per hour after how many hours would both candles be the same height