120+70+(16x-5)(20x-5)=360

Solution for 120+70+(16x-5)(20x-5)=360 equation:

120+70+(16x-5)(20x-5)=360

We move all terms to the left:

120+70+(16x-5)(20x-5)-(360)=0

We add all the numbers together, and all the variables

(16x-5)(20x-5)-170=0

We multiply parentheses ..

(+320x^2-80x-100x+25)-170=0

We get rid of parentheses

320x^2-80x-100x+25-170=0

We add all the numbers together, and all the variables

320x^2-180x-145=0

a = 320; b = -180; c = -145;
Δ = b2-4ac
Δ = -1802-4·320·(-145)
Δ = 218000
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:

$\sqrt{\Delta}=\sqrt{218000}=\sqrt{400*545}=\sqrt{400}*\sqrt{545}=20\sqrt{545}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-180)-20\sqrt{545}}{2*320}=\frac{180-20\sqrt{545}}{640}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-180)+20\sqrt{545}}{2*320}=\frac{180+20\sqrt{545}}{640}
$