24=24t-4.9t^2

Solution for 24=24t-4.9t^2 equation:

24=24t-4.9t^2

We move all terms to the left:

24-(24t-4.9t^2)=0

We get rid of parentheses

4.9t^2-24t+24=0

a = 4.9; b = -24; c = +24;
Δ = b2-4ac
Δ = -242-4·4.9·24
Δ = 105.6
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-24)-\sqrt{105.6}}{2*4.9}=\frac{24-\sqrt{105.6}}{9.8}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-24)+\sqrt{105.6}}{2*4.9}=\frac{24+\sqrt{105.6}}{9.8}
$