color(red)(-6y+3x=2) can be rewritten as color(red)(y=1/2x-1/3)
When x=5
color(white)("XXX")y=1/2x-1/3color(white)("XX")rarrcolor(white)("XX")y=color(red)(13/6)
The vertical distance from color(green)(""(5,1)) to the point color(red)(""(5,13/6)) on the line color(red)(-6y+3x=2) is
color(white)("XXX")color(blue)(13/6-1=7/6)
That is moving vertically the line color(red)(-6y+3x=2) is color(blue)(7/6) above the point color(green)(""(5,1)).
If we continue moving upward another color(blue)(7/6) units (for a total of 14/6=7/3 units above color(green)(""(5,1)))
we will reach the point ""(5,10/3))
which will be the same distance above color(red)(-6y+3x=2) as color(green)(""(5,1)) is below it.
That is color(red)(-6y+3x=2) bisects the line segment joining color(green)(""(5,1)) and color(purple)(""(5,10/3))
In fact the line segment between color(green)(""(5,1)) and any point on the line parallel to color(red)(-6y+3x=2) through color(purple)(""(5,10/3)) will be bisected by color(red)(-6y+3x=2)
color(red)(-6y+3x=2) has a slope of color(red)(1/2)
so the line through color(purple)(""(5,10/3)) will also have a slope of color(red)(1/2)
and using the slope-point form, it will have an equation of
color(white)("XXX")y-color(purple)(10/3)=color(red)(1/2)(x-color(purple)(5))
which can be simplified as
color(white)("XXX")y=x/2+5/6