13=2x+0.6x^2

Solution for 13=2x+0.6x^2 equation:

13=2x+0.6x^2

We move all terms to the left:

13-(2x+0.6x^2)=0

We get rid of parentheses

-0.6x^2-2x+13=0

a = -0.6; b = -2; c = +13;
Δ = b2-4ac
Δ = -22-4·(-0.6)·13
Δ = 35.2
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{35.2}}{2*-0.6}=\frac{2-\sqrt{35.2}}{-1.2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-2)+\sqrt{35.2}}{2*-0.6}=\frac{2+\sqrt{35.2}}{-1.2}
$