Answer :
//I'm going to use differentiation to show you how to do this, although I would normally use mechanics.
dh/dt = -32t + 24
-32t + 24 = 0 when maximum
32t = 24
t = 24/32
t = 3/4
//To find the maximum height just substitute "t" in
h = -16 (9/16) + 24(3/4) + 7
h = -9 + 18 + 7
h = 16ft
dh/dt = -32t + 24
-32t + 24 = 0 when maximum
32t = 24
t = 24/32
t = 3/4
//To find the maximum height just substitute "t" in
h = -16 (9/16) + 24(3/4) + 7
h = -9 + 18 + 7
h = 16ft