daca e exercitiul 8 atunci :
1/2-1/7=7/14-2/14=5/14(14 este divizorul comun)
2/3-1/4=8/12-3/12=5/12
5/6-1/3=15/18-6/18=9/18
7/2-1/5=35/10-2/10=33/10
2/3-1/2=4/6-3/6=1/6
11/4-3/2=22/8-12/8=10/8
11/12-5/18=198/216-60/216=138/216
13/20-7/30=39/60-14/60=25/60
sper ca e bine ca nu prea se intelegea
