.07x.10(800-x)=74

Solution for .07x.10(800-x)=74 equation:

.07x.10(800-x)=74

We move all terms to the left:

.07x.10(800-x)-(74)=0

We add all the numbers together, and all the variables

.07x.10(-1x+800)-74=0

We multiply parentheses

-1x^2+800x-74=0

a = -1; b = 800; c = -74;
Δ = b2-4ac
Δ = 8002-4·(-1)·(-74)
Δ = 639704
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:

$\sqrt{\Delta}=\sqrt{639704}=\sqrt{4*159926}=\sqrt{4}*\sqrt{159926}=2\sqrt{159926}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(800)-2\sqrt{159926}}{2*-1}=\frac{-800-2\sqrt{159926}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(800)+2\sqrt{159926}}{2*-1}=\frac{-800+2\sqrt{159926}}{-2}
$