a)
-----------------------x------------------x----------x---------------
M N P
MP>MN, deci luam punctele in ordinea M,N,P pe dreapta
NP=MP-MN=8cm-6cm=2cm
b)
-------------------------x----------------x---------x-----------
M P N
MN>MP, deci luam punctele in ordinea M,P,N pe dreapta
NP=MN-MP=7cm-4cm=3cm