1st. Try to make x by itself. Divide 12 on each side.
After it will look like this
x=12
I have no idea what did he do
Answer: 

Step-by-step explanation:
Given :

re - writing the equation , we have

we need to find the value of a and b for which -2<x < 4 , this means that the roots of the quadratic equation are -2<x < 4.
The formula for finding the quadratic equation when the roots are known is :
- sum of roots(x) + product of root = 0
sum of roots = -2 + 4 = 2
product of roots = -2 x 4 = -8
substituting into the formula , we have:
, which could be written in inequality form as

comparing with
, it means that :


The slope between the points (x1,y1) and (x2,y2) is
slope=(y2-y1)/(x2-x1)
(0,6) and (5,-4)
x1=0
y1=6
x2=5
y2=-4
slope=(-4-6)/(5-0)=-10/5=-2
slope=-2