Addition/sub

Front 1

2 + 3=

Back 1

5

Front 2

2+ 4 =

Back 2

6

Front 3

2 + 5 =

Back 3

7

Front 4

2 + 6 =

Back 4

8

Front 5

2 + 7 =

Back 5

9

Front 6

2 + 8 =

Back 6

10

Front 7

2 + 9 =

Back 7

11

Front 8

2 + 10 =

Back 8

12

Front 9

2 + 11 =

Back 9

13

Front 10

2 + 12 =

Back 10

14

Front 11

2 + 13 =

Back 11

15

Front 12

2 + 14 =

Back 12

16

Front 13

2 + 15 =

Back 13

17

Front 14

2 + 16 =

Back 14

18

Front 15

2 + 17 =

Back 15

19

Front 16

2 + 18 =

Back 16

20