On a coordinate system, the segment joining the points (3,8) and (9,16) has the same midpoint as the line segment joining the points (8,11) and (x,13). What is the value of x?

Question

I think x=3

Answer 1

Mid-point of (3,8) and (9,16)
=((3+9)/2, (8+16)/2)
=(6,12)

Mid-point of (8,11) and (x,13)
=((8+x)/2, (11+13)/2)
=((8+x)/2, 12)

To have the same mid-point, the x- and y-coordinates of the mid points must match.
so
(8+x)/2 = 6
Solve for x.