Well us as kids are constantly on the computer and phones so google classroom is a great way to keep us connected with our teachers because we can communicate with them and they with us by posting assignments. Therefore we are less likely to forget what they told us in the classroom because it is just one click away.
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.
The equation of the line that passes through the points (2,1) and (5,-8) is
y = -3x + 7
(-5,2) concave up
Hope this helps :)