x(56-9x)=12

Solution for x(56-9x)=12 equation:

x(56-9x)=12

We move all terms to the left:

x(56-9x)-(12)=0

We add all the numbers together, and all the variables

x(-9x+56)-12=0

We multiply parentheses

-9x^2+56x-12=0

a = -9; b = 56; c = -12;
Δ = b2-4ac
Δ = 562-4·(-9)·(-12)
Δ = 2704
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2704}=52$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(56)-52}{2*-9}=\frac{-108}{-18}
=+6
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(56)+52}{2*-9}=\frac{-4}{-18}
=2/9
$