Answer:
10 units
Step-by-step explanation:
LMNO is a square.
All sides of square are equal
MN = LM
3x + 1 = x + 7
3x - x = 7 - 1
2x = 6
x = 6/2
x = 3
LM = x + 7 = 3 + 7 = 10
LM = 10 units
