Since point M is the midpoint of LN, LM and MN are equivalent in length.
7x - 12 = 3x + 16 (LM=MN)
7x = 3x + 28
4x = 28
x = 7
Now that we know the value of x, we can find the value of LM by plugging the value in the equation.
LM = 7(7) - 12
LM = 49 - 12
LM = 37