X*(x+20)=1500

Solution for X*(x+20)=1500 equation:

X(X+20)=1500

We move all terms to the left:

X(X+20)-(1500)=0

We multiply parentheses

X^2+20X-1500=0

a = 1; b = 20; c = -1500;
Δ = b2-4ac
Δ = 202-4·1·(-1500)
Δ = 6400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{6400}=80$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(20)-80}{2*1}=\frac{-100}{2}
=-50
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(20)+80}{2*1}=\frac{60}{2}
=30
$