The problem indicates that the ball was thrown horizontally. Therefore Vox is 24 m/s and Voy = 0
Yo = initial eight where the ball is coming from
Y is the final height or the ground
The formula will be like this,
Y=Yo+Voy t- (1/2) gt^2 with that said Voy t = 0 since Voy=0,
With the height or Y = 0
0=Yo-(1/2)gt^2
Yo= (1/2)gt^2
then solve the equation and it will look like this,
Yo= (1/2)(9.8 m/s^2)[(4s)^2]
Then the answer would be
Yo = 78.4 m