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