Răspuns:
a+1/3=2/3 a=2/3-1/3 a=1/3
a-1/2=1/2. a=1/2+1/2. a=2/2 a=1
a+1/7+2/7=6/7 a=6/7-1/7-2/7 a=3/7
3/5+a=4/5. a=4/5-3/5. a=2/5
6/9-a=2/9 a=6/9-2/9. a=7/9
1/10+7/10-a=4/10. 17/10-4/10=a
a=13/10
a+3/7=5/7. a=5/7-3/7. a=2/7
a-1/7=2/7. a=2/7+1/7. a=3/7
a-(1/4+1/4)=1/4. a-2/4=1/4
a=1/4+2/4. a=3/4
