Mr. Linn is standing 50m from a large bell. With his mighty throwing arm, Mr. Linn throws a rock at the bell and he hears the sound of the bell 4.5 s later. If the speed of the sound is 330m/s, what was the speed of the rock in the air?

Answer 1

I expect that you are to consider only the rock's horizontal speed.
In that case, just recall that time = distance/speed.
So, if the rock's speed was x m/s, we need the total round-trip time of rock and sound to be 4.5 s. That means we have to solve
50/x + 50/330 = 4.5
x = 11.5 m/s