I remember seeing this problem in Alcumus, or maybe a similar variation of it. However, the solution is pretty simple.

set y = 0, since we are trying to find out when the ball hits the ground, and when that happens, Y = 0.

This looks like a quadratic formula!

\(0 = -16t^2 + 26t + 105\)

Then, simply solve for this quadratic. There will be two answers, but one of them is negative, so choose the postitve answer.

\(\frac{-26 +\sqrt{26^2 - 4(-16)(105)} }{2(-16)}\)

That should be the postive answer. Sorry, it's a little messy. Solve this equation and the answer shall be the final answer!

Hope this helps!