Answer:
Given the projectile formula:

where, t is the time in second.
As per the statement:
A quarterback throws a football toward a receiver from a height of 6 ft. The initial vertical velocity of the ball is 14 ft/s
⇒
and v= 14 ft/s
Substitute these given values we have;

It is also given that at the same time that the ball is thrown, the receiver raises his hands to a height of 8 ft and jumps up with an initial vertical velocity of 10 ft/s.
⇒
and v= 10 ft/s
then;

Therefore, the system that models the heights of the ball and the receiver's hands over time :

