20=80x-16x^2

Solution for 20=80x-16x^2 equation:

20=80x-16x^2

We move all terms to the left:

20-(80x-16x^2)=0

We get rid of parentheses

16x^2-80x+20=0

a = 16; b = -80; c = +20;
Δ = b2-4ac
Δ = -802-4·16·20
Δ = 5120
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{5120}=\sqrt{1024*5}=\sqrt{1024}*\sqrt{5}=32\sqrt{5}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-80)-32\sqrt{5}}{2*16}=\frac{80-32\sqrt{5}}{32}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-80)+32\sqrt{5}}{2*16}=\frac{80+32\sqrt{5}}{32}
$