Question 1133975
I'm a bit confused about the results from the equation for height that was given.  However...here is what I've come up with.
a. t = 3 sec
y = -16(3)^2 + 144
y = 0 ft (The shell hits the ground at 3 seconds)
b.  t = 3 sec
x = 39(3)
x = 117 ft
c.  t = 4.5 sec (I don't agree that this is when it reaches it's maximum height since it hit the ground at 3 sec and the answer to this is negative)
y = -16(4.5)^2 + 144 = -180 ft
d.  x = 39(4.5) = 175.5 ft (although this doesn't make sense based on previous answers)