Условие:
1. 53+7
2. 86+4
3. 56+6
4. 47+9
5. 8+16
6. 60-9
7. 70-3
8. 80-18
9. 60-17
10. 90-12
11. 400-9
12. 100-7
13. 11-5
14. 13-9
15. 17-8
16. 12-4
17. 46-7
18. 61-6
19. 54-19
20. 85-47
Решение:
\[\boxed{\mathbf{1.}}\]
\[53 + 7 = 60\]
\[\boxed{\mathbf{2.}}\]
\[86 + 4 = 90\]
\[\boxed{\mathbf{3.}}\]
\[56 + 6 = 62\]
\[\boxed{\mathbf{4.}}\]
\[47 + 9 = 56\]
\[\boxed{\mathbf{5.}}\]
\[8 + 16 = 24\]
\[\boxed{\mathbf{6.}}\]
\[60 - 9 = 51\]
\[\boxed{\mathbf{7.}}\]
\[70 - 3 = 67\]
\[\boxed{\mathbf{8.}}\]
\[80 - 18 = 62\]
\[\boxed{\mathbf{9.}}\]
\[60 - 17 = 43\]
\[\boxed{\mathbf{10.}}\]
\[90 - 12 = 78\]
\[\boxed{\mathbf{11.}}\]
\[400 - 9 = 391\]
\[\boxed{\mathbf{12.}}\]
\[100 - 7 = 93\]
\[\boxed{\mathbf{13.}}\]
\[11 - 5 = 6\]
\[\boxed{\mathbf{14.}}\]
\[13 - 9 = 4\]
\[\boxed{\mathbf{15.}}\]
\[17 - 8 = 9\]
\[\boxed{\mathbf{16.}}\]
\[12 - 4 = 8\]
\[\boxed{\mathbf{17.}}\]
\[46 - 7 = 39\]
\[\boxed{\mathbf{18.}}\]
\[61 - 6 = 55\]
\[\boxed{\mathbf{19.}}\]
\[54 - 19 = 35\]
\[\boxed{\mathbf{20.}}\]
\[85 - 47 = 38\]