(x+40)(3x)=180

Solution for (x+40)(3x)=180 equation:

(x+40)(3x)=180

We move all terms to the left:

(x+40)(3x)-(180)=0

We multiply parentheses

3x^2+120x-180=0

a = 3; b = 120; c = -180;
Δ = b2-4ac
Δ = 1202-4·3·(-180)
Δ = 16560
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:

$\sqrt{\Delta}=\sqrt{16560}=\sqrt{144*115}=\sqrt{144}*\sqrt{115}=12\sqrt{115}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(120)-12\sqrt{115}}{2*3}=\frac{-120-12\sqrt{115}}{6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(120)+12\sqrt{115}}{2*3}=\frac{-120+12\sqrt{115}}{6}
$