midpoint formula
mid of (x1,y1) and (x2,y2) is
[tex]( \frac{x2+x1}{2}, \frac{y2+y1}{2}) [/tex]
so
(22,15)=[tex]( \frac{18+x1}{2}, \frac{6+y1}{2}) [/tex]
therefor
22=[tex] \frac{18+x1}{2} [/tex]
and
15=[tex] \frac{6+y1}{2} [/tex]
slv each
22=[tex] \frac{18+x1}{2} [/tex]
times both sides by 2
44=18+x1
minus 18 both sides
26=x1
15=[tex] \frac{6+y1}{2} [/tex]
times both sides by 2
30=6+y1
minus 6
24=y1
the other point is (26,24)