We can use the middle point equation:
[tex]\begin{gathered} Mp=(xm,ym) \\ where\colon \\ xm=\frac{x1+x2}{2} \\ ym=\frac{y1+y2}{2} \end{gathered}[/tex]Let:
[tex]\begin{gathered} J=(x1,y1)=(5,7) \\ K=(x2,y2)=(3,9) \end{gathered}[/tex]so:
[tex]\begin{gathered} xm=\frac{5+3}{2}=\frac{8}{2}=4 \\ ym=\frac{7+9}{2}=\frac{16}{2}=8 \end{gathered}[/tex]Therefore, the middle point is:
[tex]Mp=(xm,ym)=(4,8)[/tex]