Question 587363
{{{ x = -7 }}} is a vertical line through (-7,0)
Think of the equation as saying: " I am a line
that always sees {{{-7}}} on the x-axis, and
I don't care what {{{y}}} is."
Any line perpendicular to this line will be a horizontal 
line which means it has slope = {{{0}}}.
If the general form of an equation is {{{ y = m*x + b }}},
where {{{m}}} = slope, then I have
{{{ y = 0*x + b }}}
{{{ y = b }}}
The line goes through (0,2), which is on the y-axis
It intersects the given vertical line {{{ x = -7 }}} at
(-7,2). Both these points tell me that the equation is
{{{ y = 2 }}}