(0.4x)(0.75x-2)=180

Solution for (0.4x)(0.75x-2)=180 equation:

(0.4x)(0.75x-2)=180

We move all terms to the left:

(0.4x)(0.75x-2)-(180)=0

We add all the numbers together, and all the variables

(+0.4x)(0.75x-2)-180=0

We multiply parentheses ..

(+0x^2+0x)-180=0

We get rid of parentheses

0x^2+0x-180=0

We add all the numbers together, and all the variables

x^2+x-180=0

a = 1; b = 1; c = -180;
Δ = b2-4ac
Δ = 12-4·1·(-180)
Δ = 721
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{-(1)-\sqrt{721}}{2*1}=\frac{-1-\sqrt{721}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1)+\sqrt{721}}{2*1}=\frac{-1+\sqrt{721}}{2}
$