X(x+20)=30

Solution for X(x+20)=30 equation:

X(X+20)=30

We move all terms to the left:

X(X+20)-(30)=0

We multiply parentheses

X^2+20X-30=0

a = 1; b = 20; c = -30;
Δ = b2-4ac
Δ = 202-4·1·(-30)
Δ = 520
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{520}=\sqrt{4*130}=\sqrt{4}*\sqrt{130}=2\sqrt{130}$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(20)-2\sqrt{130}}{2*1}=\frac{-20-2\sqrt{130}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(20)+2\sqrt{130}}{2*1}=\frac{-20+2\sqrt{130}}{2}
$