(50-x)*(30-x)=1125

Solution for (50-x)*(30-x)=1125 equation:

(50-x)(30-x)=1125

We move all terms to the left:

(50-x)(30-x)-(1125)=0

We add all the numbers together, and all the variables

(-1x+50)(-1x+30)-1125=0

We multiply parentheses ..

(+x^2-30x-50x+1500)-1125=0

We get rid of parentheses

x^2-30x-50x+1500-1125=0

We add all the numbers together, and all the variables

x^2-80x+375=0

a = 1; b = -80; c = +375;
Δ = b2-4ac
Δ = -802-4·1·375
Δ = 4900
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{4900}=70$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-80)-70}{2*1}=\frac{10}{2}
=5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-80)+70}{2*1}=\frac{150}{2}
=75
$