13-(     )=6

18-(     )=7

13-(     )=10

16-(     )=14

15-(     )=7

11-(     )=10

13-(     )=13

20-(     )=12

12-(     )=9

20-(     )=4

13-(     )=4

12-(     )=9

16-(     )=9

12-(     )=6

12-(     )=9

20-(     )=18

16-(     )=16

13-(     )=10

18-(     )=8

14-(     )=12

13-(     )=3

11-(     )=1

16-(     )=9

19-(     )=14

19-(     )=17

11-(     )=2

17-(     )=13

17-(     )=12

13-(     )=8

11-(     )=10

18-(     )=10

14-(     )=1

18-(     )=3

12-(     )=5

15-(     )=2

13-(     )=5

20-(     )=7

20-(     )=7

14-(     )=14

12-(     )=11

16-(     )=8

16-(     )=10

12-(     )=7

18-(     )=7

20-(     )=3

20-(     )=8

13-(     )=6

17-(     )=12

14-(     )=8

19-(     )=0