7/5-a=2/5
a=7/5-2/5
a=5/5
b+3/9=1 (un intreg)
b+3/9=9/9
b=9/9-3/9
b=6/9
(c+7/8)+2/8=10/8
c+7/8=10/8-2/8
c+7/8=8/8
c=8/8-7/8
c=1/8
(2/10+2/10+d)-1/10=5/10
4/10+d=5/10+1/10
4/10+d=6/10
d=6/10-4/10
d=2/10
(12/6-7/6)+2/6-(e+1)=0
5/6+2/6-(e+1)=0
7/6-(e+6/6)=0
e+6/6=7/6
e=7/6-6/6
e=1/6
(13/5+7/5)-(10/5+2/5)=f+5/5
20/5-12/5=f+5/5
8/5=f+5/5
f=8/5-5/5
f=3/5
