Question 162368
Remember that each point is an (x,y) that completely satisfies 
the equation.
The general equation for a line is {{{y = mx + b}}}.
You can plug in the x and y for each point and then
solve for m and b. You don't even have to know what
m and b are to do this
The points are (-7,9) and (8,9)
{{{y = mx + b}}}
(1) {{{9 = m*(-7) + b}}}
(2) {{{9 = m*8 + b}}}
Now subtract (2) from (1), being careful of signs
{{{0 = -7m - 8m + b - b}}}
{{{-15m = 0}}}
{{{m = 0}}}
If {{{m = 0}}} in either (1) or (2), then
{{{b = 9}}}
Now write an equation for the line using the facts
{{{m = 0}}}
{{{b = 9}}}
{{{y = mx + b}}}
{{{y = 0*x + 9}}}
{{{y = 9}}} 
This is the equation of the line. It is a horizontal line
where y is always {{{9}}} and x can be anything in either
the (+) or (-) direction.
You can practice this method. Just pick any two points
and do what I did.