(18-x)*(18-3x)=0

Solution for (18-x)*(18-3x)=0 equation:

(18-x)(18-3x)=0

We add all the numbers together, and all the variables

(-1x+18)(-3x+18)=0

We multiply parentheses ..

(+3x^2-18x-54x+324)=0

We get rid of parentheses

3x^2-18x-54x+324=0

We add all the numbers together, and all the variables

3x^2-72x+324=0

a = 3; b = -72; c = +324;
Δ = b2-4ac
Δ = -722-4·3·324
Δ = 1296
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1296}=36$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-72)-36}{2*3}=\frac{36}{6}
=6
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-72)+36}{2*3}=\frac{108}{6}
=18
$