So, h(t) is how far is Daniel's head from the surface of the water, namely the surface itself is when the height is nill, so his head is at the surface and the height of it is just 0, thus h(t) = 0. Namely, what is "t" when h(t) is 0?

clearly the seconds cannot be a negative unit, so is not -3/2.
Separate it into two different shapes
36 is a perfect square, but its factors include 1 and 36, 6 and 6, 4 and 9, 3 and 12, and 2 and 18. that's 9 factors, not 3.