(x+0.8)*(55-x)=55

Solution for (x+0.8)*(55-x)=55 equation:

(x+0.8)(55-x)=55

We move all terms to the left:

(x+0.8)(55-x)-(55)=0

We add all the numbers together, and all the variables

(x+0.8)(-1x+55)-55=0

We multiply parentheses ..

(-1x^2+55x-0.8x+44)-55=0

We get rid of parentheses

-1x^2+55x-0.8x+44-55=0

We add all the numbers together, and all the variables

-1x^2+54.2x-11=0

a = -1; b = 54.2; c = -11;
Δ = b2-4ac
Δ = 54.22-4·(-1)·(-11)
Δ = 2893.64
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(54.2)-\sqrt{2893.64}}{2*-1}=\frac{-54.2-\sqrt{2893.64}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(54.2)+\sqrt{2893.64}}{2*-1}=\frac{-54.2+\sqrt{2893.64}}{-2}
$