50=0.03x^2+3x+3.5

Solution for 50=0.03x^2+3x+3.5 equation:

50=0.03x^2+3x+3.5

We move all terms to the left:

50-(0.03x^2+3x+3.5)=0

We get rid of parentheses

-0.03x^2-3x-3.5+50=0

We add all the numbers together, and all the variables

-0.03x^2-3x+46.5=0

a = -0.03; b = -3; c = +46.5;
Δ = b2-4ac
Δ = -32-4·(-0.03)·46.5
Δ = 14.58
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{-(-3)-\sqrt{14.58}}{2*-0.03}=\frac{3-\sqrt{14.58}}{-0.06}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-3)+\sqrt{14.58}}{2*-0.03}=\frac{3+\sqrt{14.58}}{-0.06}
$