200=0.008x^2+0.518x+131.886

Solution for 200=0.008x^2+0.518x+131.886 equation:

200=0.008x^2+0.518x+131.886

We move all terms to the left:

200-(0.008x^2+0.518x+131.886)=0

We get rid of parentheses

-0.008x^2-0.518x-131.886+200=0

We add all the numbers together, and all the variables

-0.008x^2-0.518x+68.114=0

a = -0.008; b = -0.518; c = +68.114;
Δ = b2-4ac
Δ = -0.5182-4·(-0.008)·68.114
Δ = 2.447972
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{-(-0.518)-\sqrt{2.447972}}{2*-0.008}=\frac{0.518-\sqrt{2.447972}}{-0.016}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-0.518)+\sqrt{2.447972}}{2*-0.008}=\frac{0.518+\sqrt{2.447972}}{-0.016}
$