60=(3x+6)(x+5)

Solution for 60=(3x+6)(x+5) equation:

60=(3x+6)(x+5)

We move all terms to the left:

60-((3x+6)(x+5))=0

We multiply parentheses ..

-((+3x^2+15x+6x+30))+60=0


We calculate terms in parentheses: -((+3x^2+15x+6x+30)), so:

(+3x^2+15x+6x+30)

We get rid of parentheses

3x^2+15x+6x+30

We add all the numbers together, and all the variables

3x^2+21x+30

Back to the equation:

-(3x^2+21x+30)


We get rid of parentheses

-3x^2-21x-30+60=0

We add all the numbers together, and all the variables

-3x^2-21x+30=0

a = -3; b = -21; c = +30;
Δ = b2-4ac
Δ = -212-4·(-3)·30
Δ = 801
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:

$\sqrt{\Delta}=\sqrt{801}=\sqrt{9*89}=\sqrt{9}*\sqrt{89}=3\sqrt{89}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-21)-3\sqrt{89}}{2*-3}=\frac{21-3\sqrt{89}}{-6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-21)+3\sqrt{89}}{2*-3}=\frac{21+3\sqrt{89}}{-6}
$