60=x^2+6x-135

Solution for 60=x^2+6x-135 equation:

60=x^2+6x-135

We move all terms to the left:

60-(x^2+6x-135)=0

We get rid of parentheses

-x^2-6x+135+60=0

We add all the numbers together, and all the variables

-1x^2-6x+195=0

a = -1; b = -6; c = +195;
Δ = b2-4ac
Δ = -62-4·(-1)·195
Δ = 816
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:

$\sqrt{\Delta}=\sqrt{816}=\sqrt{16*51}=\sqrt{16}*\sqrt{51}=4\sqrt{51}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-6)-4\sqrt{51}}{2*-1}=\frac{6-4\sqrt{51}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-6)+4\sqrt{51}}{2*-1}=\frac{6+4\sqrt{51}}{-2}
$