The first thing to do is to imagine the situation. OK, cone draining at a certain rate into a cylinder. Is the cylinder lying on its side? Who knows, it doesn't say.
Careless of them, but not atypical. In real work, one gets a lot of irrelevant information, and the relevant bits are all too often missing.
And we don't know how much water was in the cone to begin with. That makes a big difference. So let us assume the cylinder is circular base down, like my hot water tank.
We are asked about the rate of increase in water level in the cylinder when the water level in the cone is whatever.
Who cares about how high the water is in the cone? Not I, the cylinder is filling at constant rate. Now it's over, minor calculation.
Remark: The above, though formula-free, is mathematics. If you end up doing any consulting, you will find that the majority of problems do not involve high level mathematics. And yet the perspective of a professional mathematician may be precisely what is needed, even if in principle the technical level is very low.