Adding fractions with the same denomenator
subtracting fractions

100

5/10 + 2/10

7/10

100

5/10-2/10

3/10

200

1/15 + 7/15

8/15

200

9/15-7/15

2/15

300

10/20 + 5/20

15/20

300

15/20-8/20

7/20

400

17/30 + 8/30

25/30

400

20/30-9/30

11/30