.75x(.8x-2)=2.75

Solution for .75x(.8x-2)=2.75 equation:

.75x(.8x-2)=2.75

We move all terms to the left:

.75x(.8x-2)-(2.75)=0

We add all the numbers together, and all the variables

.75x(.8x-2)-2.75=0

We multiply parentheses

x^2-2x-2.75=0

a = 1; b = -2; c = -2.75;
Δ = b2-4ac
Δ = -22-4·1·(-2.75)
Δ = 15
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{-(-2)-\sqrt{15}}{2*1}=\frac{2-\sqrt{15}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-2)+\sqrt{15}}{2*1}=\frac{2+\sqrt{15}}{2}
$