(30-2x)*(20-2x)=264

Solution for (30-2x)*(20-2x)=264 equation:

(30-2x)(20-2x)=264

We move all terms to the left:

(30-2x)(20-2x)-(264)=0

We add all the numbers together, and all the variables

(-2x+30)(-2x+20)-264=0

We multiply parentheses ..

(+4x^2-40x-60x+600)-264=0

We get rid of parentheses

4x^2-40x-60x+600-264=0

We add all the numbers together, and all the variables

4x^2-100x+336=0

a = 4; b = -100; c = +336;
Δ = b2-4ac
Δ = -1002-4·4·336
Δ = 4624
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{4624}=68$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-100)-68}{2*4}=\frac{32}{8}
=4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-100)+68}{2*4}=\frac{168}{8}
=21
$