0=200x-0.3x^2

Solution for 0=200x-0.3x^2 equation:

0=200x-0.3x^2

We move all terms to the left:

0-(200x-0.3x^2)=0

We add all the numbers together, and all the variables

-(200x-0.3x^2)=0

We get rid of parentheses

0.3x^2-200x=0

a = 0.3; b = -200; c = 0;
Δ = b2-4ac
Δ = -2002-4·0.3·0
Δ = 40000
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{40000}=200$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-200)-200}{2*0.3}=\frac{0}{0.6}
=0
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-200)+200}{2*0.3}=\frac{400}{0.6}
=666+0.40000000000003/0.6
$