Given:
[tex]\begin{gathered} LN=54 \\ LM=31 \end{gathered}[/tex]Required:
To find the value of MN.
Explanation:
Consider the figure
From the figure
[tex]\begin{gathered} LN=LM+MN \\ \\ 54=31+MN \\ \\ MN=54-31 \\ \\ MN=23 \end{gathered}[/tex]Final Answer:
[tex]MN=23[/tex]