A line segment has a midpoint of (6, 4) and an endpoint of (2, 1). What is the other endpoint of the line segment?

We have

(2 + x) / 2 = 6        and   (1 + y) / 2  = 4

2 + x   = 12                      1  +  y  = 8

x = 10                                  y = 7

So...the other endpoint is    (10. 7)