X(3x+2)=90

Solution for X(3x+2)=90 equation:

X(3X+2)=90

We move all terms to the left:

X(3X+2)-(90)=0

We multiply parentheses

3X^2+2X-90=0

a = 3; b = 2; c = -90;
Δ = b2-4ac
Δ = 22-4·3·(-90)
Δ = 1084
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:

$\sqrt{\Delta}=\sqrt{1084}=\sqrt{4*271}=\sqrt{4}*\sqrt{271}=2\sqrt{271}$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(2)-2\sqrt{271}}{2*3}=\frac{-2-2\sqrt{271}}{6}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(2)+2\sqrt{271}}{2*3}=\frac{-2+2\sqrt{271}}{6}
$