-7x+3x(x-6)=-20

Solution for -7x+3x(x-6)=-20 equation:

-7x+3x(x-6)=-20

We move all terms to the left:

-7x+3x(x-6)-(-20)=0

We add all the numbers together, and all the variables

-7x+3x(x-6)+20=0

We multiply parentheses

3x^2-7x-18x+20=0

We add all the numbers together, and all the variables

3x^2-25x+20=0

a = 3; b = -25; c = +20;
Δ = b2-4ac
Δ = -252-4·3·20
Δ = 385
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-25)-\sqrt{385}}{2*3}=\frac{25-\sqrt{385}}{6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-25)+\sqrt{385}}{2*3}=\frac{25+\sqrt{385}}{6}
$