Addition
Subtraction
add/sub
100

2/3 + 1/2

1 1/6 or 7/6

100

2/3 - 1/2

1/6

100

2/3 + 4/6 - 3/6

5/6

300

4/5  + 7/12

1 23/60 or 83/60

300

4/5 -7/12

13/60

500

2/3 + 4/6 +2/8

1 14/24 or 38/24

500

2/3 - 4/6 - 2/8

2/8

700

9/12 + 2/6

1 1/12 or 13/12