what conclusion can be drawn by observing that 5 is to the left of 10 on a number line
A number, say 'x' is to the left of 10, then x is less than 10. x could be anything from 9.9999999999 to negative infinity. In this case, 5 is clearly less than 10 and is a midpoint of the line segment starting at origin and ending at 10.
If you draw perpendicular bisector of the line segment with origin and 10 as endpoints then that perpendicular bisector would pass through 5 (a fancy way of saying 5 is a midpoint).
