24=-16t^2+56t

Solution for 24=-16t^2+56t equation:

24=-16t^2+56t

We move all terms to the left:

24-(-16t^2+56t)=0

We get rid of parentheses

16t^2-56t+24=0

a = 16; b = -56; c = +24;
Δ = b2-4ac
Δ = -562-4·16·24
Δ = 1600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1600}=40$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-56)-40}{2*16}=\frac{16}{32}
=1/2
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-56)+40}{2*16}=\frac{96}{32}
=3
$