Since the rate of change or the rate at which the pool gets filled up is 30 grams per minute we could say that it fills up in 30(m) since it already has 1500g in the pool and the maximum amount of water it could hold is 4500 so the amount of water that must be at the pool after m minutes is less than or equal to 4500. Therefore the equation will look like this

if you solve the inequality you will have that

In other words, it will take at the most 100 minutes for the pool to fill up to 4500