From the diagram we can conclude:
[tex]m\angle JKM=m\angle JKL+m\angle LKN+m\angle NKM[/tex]Since KN bisects bisects ∠LKM:
[tex]\begin{gathered} m\angle LKN=m\angle NKM \\ so\colon \\ m\angle LKM=2m\angle LKN \\ m\angle LKN=\frac{m\angle LKM}{2} \\ m\angle LKN=\frac{40}{2} \\ m\angle LKN=20 \end{gathered}[/tex]Therefore:
[tex]\begin{gathered} 73=m\angle JKL+20+20 \\ m\angle JKL=73-20-20 \\ m\angle JKL=33 \end{gathered}[/tex]Hence:
[tex]\begin{gathered} m\angle JKN=m\angle JKL+m\angle LKN \\ m\angle JKN=33+20 \\ m\angle JKN=53 \end{gathered}[/tex]