Условие:

8 + ☐ = 3520;
9 + ☐ = 5740;
6 + ☐ = 2410;
18 − ☐ = 2920;
12 − ☐ = 6056;
11 − ☐ = 9590;
☐ − 8 = 3630;
☐ − 7 = 4943;
☐ − 5 = 189.

8 + ☐ = 3520
8 + ☐ = 15
☐ = 158
☐ = 7
8 + 7 = 3520
15 = 15
 
9 + ☐ = 5740
9 + ☐ = 17
☐ = 179
☐ = 8
9 + 8 = 5740
17 = 17
 
6 + ☐ = 2410
6 + ☐ = 14
☐ = 146
☐ = 8
6 + 8 = 2410
14 = 14
 
18 − ☐ = 2920
18 − ☐ = 9
☐ = 189
☐ = 9
189 = 2920
9 = 9
 
12 − ☐ = 6056
12 − ☐ = 4
☐ = 124
☐ = 8
128 = 6056
4 = 4
 
11 − ☐ = 9590
11 − ☐ = 5
☐ = 115
☐ = 6
116 = 9590
5 = 5
 
☐ − 8 = 3630
☐ − 8 = 6
☐ = 6 + 8
☐ = 14
148 = 3630
6 = 6
 
☐ − 7 = 4943
☐ − 7 = 6
☐ = 6 + 7
☐ = 13
137 = 4943
6 = 6
 
☐ − 5 = 189
☐ − 5 = 9
☐ = 9 + 5
☐ = 14
145 = 189
9 = 9