X(13-2x)=15

Solution for X(13-2x)=15 equation:

X(13-2X)=15

We move all terms to the left:

X(13-2X)-(15)=0

We add all the numbers together, and all the variables

X(-2X+13)-15=0

We multiply parentheses

-2X^2+13X-15=0

a = -2; b = 13; c = -15;
Δ = b2-4ac
Δ = 132-4·(-2)·(-15)
Δ = 49
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{49}=7$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(13)-7}{2*-2}=\frac{-20}{-4}
=+5
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(13)+7}{2*-2}=\frac{-6}{-4}
=1+1/2
$