From the given graph:
the length of GH = 7 ⇒ distance between the points (-3,-4) and (4,-4)
the length of FH = 4√2 ⇒distance between the points (4,-4) and (0,0)
the length of FG = 5 ⇒distance between the points (-3,-4) and (0,0)
∵ ΔLMN is congruent to ΔFGH ⇒⇒⇒ ΔLMN = ΔFGH
∴ corresponding parts of congruent triangles are congruent
∴ LM = FG = 5
MN = GH = 7
LN = FH = 4√2
So, the length of side LM is 5 Units