31.07. 6+7 15-9 4+13 12-3 11+1 7-6 18-13 14+4 3+9

Решение:

6 + 7 = 13

15 - 9 = 6

4 + 13 = 17

12 - 3 = 9

11 + 1 = 12

7 - 6 = 1

18 - 13 = 5

14 + 4 = 18

3 + 9 = 12