addition and subtraction

4:19

24:37

7:27

12:54

8:32

15:26

6:12

13:43

4:07

9:53

4:43

6:07

5:57

7:06

13:14

7:16

17:53

1:38:22

45:36

11:08

59:22

21:42

5:31

7:43

23:42

22:06

11:04

1:02:48

3:12

13:46

2:28

00:59

24:53

8:59

1:44

11:20

4:23

4:07

53:48

5:35

2:23

2:34

3:26

2:14

7:57

12:32

6:10

8:35

3:20

8:26

8:32

5:32

2:27

24:57

4:53

9:06

4:39

8:55

8:46

19:35