LN + NM = LM
(3x - 12) + NM = 20
NM= 20 - 3x +12
Now replace NM = MN
x - 2= 20 - 3x + 12
Now find x
x + 3x = 20 + 12 + 2
4x = 34
x= 34/4= 17/2= 8.5
Now replace x in MN
MN= x-2 = 8.5 - 2= 6.5
Then
MN= 6.5
