0.3s+2(s-0.5)1.3s=15

Solution for 0.3s+2(s-0.5)1.3s=15 equation:

0.3s+2(s-0.5)1.3s=15

We move all terms to the left:

0.3s+2(s-0.5)1.3s-(15)=0

We multiply parentheses

2s^2+0.3s-1s-15=0

We add all the numbers together, and all the variables

2s^2-0.7s-15=0

a = 2; b = -0.7; c = -15;
Δ = b2-4ac
Δ = -0.72-4·2·(-15)
Δ = 120.49
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$s_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$s_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$s_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-0.7)-\sqrt{120.49}}{2*2}=\frac{0.7-\sqrt{120.49}}{4}
$
$s_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-0.7)+\sqrt{120.49}}{2*2}=\frac{0.7+\sqrt{120.49}}{4}
$