2x(3x-4)=30

Solution for 2x(3x-4)=30 equation:

2x(3x-4)=30

We move all terms to the left:

2x(3x-4)-(30)=0

We multiply parentheses

6x^2-8x-30=0

a = 6; b = -8; c = -30;
Δ = b2-4ac
Δ = -82-4·6·(-30)
Δ = 784
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{784}=28$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-8)-28}{2*6}=\frac{-20}{12}
=-1+2/3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-8)+28}{2*6}=\frac{36}{12}
=3
$