80=60x-0.3x^2

Solution for 80=60x-0.3x^2 equation:

80=60x-0.3x^2

We move all terms to the left:

80-(60x-0.3x^2)=0

We get rid of parentheses

0.3x^2-60x+80=0

a = 0.3; b = -60; c = +80;
Δ = b2-4ac
Δ = -602-4·0.3·80
Δ = 3504
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:

$\sqrt{\Delta}=\sqrt{3504}=\sqrt{16*219}=\sqrt{16}*\sqrt{219}=4\sqrt{219}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-60)-4\sqrt{219}}{2*0.3}=\frac{60-4\sqrt{219}}{0.6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-60)+4\sqrt{219}}{2*0.3}=\frac{60+4\sqrt{219}}{0.6}
$