(x+20)(3x)=180

Solution for (x+20)(3x)=180 equation:

(x+20)(3x)=180

We move all terms to the left:

(x+20)(3x)-(180)=0

We multiply parentheses

3x^2+60x-180=0

a = 3; b = 60; c = -180;
Δ = b2-4ac
Δ = 602-4·3·(-180)
Δ = 5760
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:

$\sqrt{\Delta}=\sqrt{5760}=\sqrt{576*10}=\sqrt{576}*\sqrt{10}=24\sqrt{10}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(60)-24\sqrt{10}}{2*3}=\frac{-60-24\sqrt{10}}{6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(60)+24\sqrt{10}}{2*3}=\frac{-60+24\sqrt{10}}{6}
$