0.75x+0.8x(x+10)=101

Solution for 0.75x+0.8x(x+10)=101 equation:

0.75x+0.8x(x+10)=101

We move all terms to the left:

0.75x+0.8x(x+10)-(101)=0

We multiply parentheses

0x^2+0.75x+0x-101=0

We add all the numbers together, and all the variables

x^2+1.75x-101=0

a = 1; b = 1.75; c = -101;
Δ = b2-4ac
Δ = 1.752-4·1·(-101)
Δ = 407.0625
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{-(1.75)-\sqrt{407.0625}}{2*1}=\frac{-1.75-\sqrt{407.0625}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1.75)+\sqrt{407.0625}}{2*1}=\frac{-1.75+\sqrt{407.0625}}{2}
$