Hello!
your three answers are:
the maximum height of the rock occurs at x=0 because the y intercept always is at x=0, and the starting point is the y intercept
the rock is in the air for 3 seconds because x goes to a max of 3
the maximum height of the rock is 45 feet because y, or height, starts at 45, and ends at 0
I hope this helps, and have a nice day!