(s-7)X0.15=5.55

Solution for (s-7)X0.15=5.55 equation:

(s-7)s0.15=5.55

We move all terms to the left:

(s-7)s0.15-(5.55)=0

We add all the numbers together, and all the variables

(s-7)s0.15-5.55=0

We multiply parentheses

s^2-7s-5.55=0

a = 1; b = -7; c = -5.55;
Δ = b2-4ac
Δ = -72-4·1·(-5.55)
Δ = 71.2
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{-(-7)-\sqrt{71.2}}{2*1}=\frac{7-\sqrt{71.2}}{2}
$
$s_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-7)+\sqrt{71.2}}{2*1}=\frac{7+\sqrt{71.2}}{2}
$