Slope-intercept form is 

y = mx + b  where the m and the b represent numbers:

y - 9 = (x + 6)

Distribute the fraction  into the parentheses:

y - 9 = x + 3

Add 9 to both sides:

    y = x + 12 

The slope is  and the y intercept is (0,12)

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First we use the slope formula:

m = 

where (x1,y1) = (11,8)
and where (x2,y2) = (-1,8)
m = 

m = 

m = 0

Point-slope formula:

y - y1 = m(x - x1)

where m = 0 and (x1,y1) = (11,8)

y - 8 = 0(x - 11)

Distribute the 0

y - 8 = 0x - 0

Add 8 to both sides:

    y = 0x + 8

You can write that without the 0x as 

y = 8 

but written that way doesn't show the slope of m = 0

Edwin