7分之1+7分之3,
=4/7

5分之1-6分之1,
=6/30-5/30
=1/30

1-3分之1,
=3/3-1/3
=2/3

8分之3+4分之1,
=3/8+2/8
=5/8

9分之5-9分之2,
=1/3

3分之1+4分之3,
=4/12+9/12
=13/12
=1又1/12

7+7分之4,
=7又4/7

6分之5-4分之3
=10/12-9/12
=1/12