a horizontal tunnel has a height of 3m. A ball is thrown inside the tunnel with an initial pseed of 18ms^-1. what is the greatest horizontal distance that the ball can travel before it bounces for the first time?

u_x=18

u_y=0

s_x=18t

s_y=-4.9t^2

thats is where i am stuck on.... I don't know what to do after this.

thanks