3x(4x-15)=180

Solution for 3x(4x-15)=180 equation:

3x(4x-15)=180

We move all terms to the left:

3x(4x-15)-(180)=0

We multiply parentheses

12x^2-45x-180=0

a = 12; b = -45; c = -180;
Δ = b2-4ac
Δ = -452-4·12·(-180)
Δ = 10665
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:

$\sqrt{\Delta}=\sqrt{10665}=\sqrt{9*1185}=\sqrt{9}*\sqrt{1185}=3\sqrt{1185}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-45)-3\sqrt{1185}}{2*12}=\frac{45-3\sqrt{1185}}{24}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-45)+3\sqrt{1185}}{2*12}=\frac{45+3\sqrt{1185}}{24}
$