Addition Doubles Plus Or Minus 1

Front 1

3+4=

Back 1

7

Front 2

0+1=

Back 2

1

Front 3

1+2=

Back 3

3

Front 4

2+1=

Back 4

3

Front 5

1+0=

Back 5

1

Front 6

3+2=

Back 6

5

Front 7

2+3=

Back 7

5

Front 8

4+3=

Back 8

7

Front 9

4+5=

Back 9

9

Front 10

5+4=

Back 10

9

Front 11

5+6=

Back 11

11

Front 12

6+5=

Back 12

11

Front 13

6+7=

Back 13

13

Front 14

7+6=

Back 14

13

Front 15

7+8=

Back 15

15

Front 16

8+7=

Back 16

15

Front 17

8+9=

Back 17

17

Front 18

9+8=

Back 18

17