Răspuns:
2/3+5/3=7/3
1/7+2/7+3/7=6/7
1/2 amplificam cu 3
iar 5/3 amplificam cu 2 deci 3/6+10/6=13/6
2/5+3/7=amplificam 2/5 cu 7 iar 3/7 cu 5 deci 14/35+15/35=29/35
2/9+7/45=amplificam 2/9 cu 5 deci 10/45+7/45=17/45
1/2+1/3+1/4=1/2 amplificam cu 6, 1/3 amplificam cu 4 iar 1/4 aplificam cu 3 deci 6/12+4/12+3/12=13/12
