30=3x(20-x*2)

Solution for 30=3x(20-x*2) equation:

30=3x(20-x*2)

We move all terms to the left:

30-(3x(20-x*2))=0

We add all the numbers together, and all the variables

-(3x(-x*2+20))+30=0


We calculate terms in parentheses: -(3x(-x*2+20)), so:

3x(-x*2+20)

We multiply parentheses

-6x^2+60x

Back to the equation:

-(-6x^2+60x)


We get rid of parentheses

6x^2-60x+30=0

a = 6; b = -60; c = +30;
Δ = b2-4ac
Δ = -602-4·6·30
Δ = 2880
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:

$\sqrt{\Delta}=\sqrt{2880}=\sqrt{576*5}=\sqrt{576}*\sqrt{5}=24\sqrt{5}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-60)-24\sqrt{5}}{2*6}=\frac{60-24\sqrt{5}}{12}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-60)+24\sqrt{5}}{2*6}=\frac{60+24\sqrt{5}}{12}
$