20 , : , .
20: 10-1, 10-2, 10-3, 10-4, 10-5, 10-6, 10-7, 10-8, 10-9.
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21: 20-1, 20-4, 20-5, 20-7, 20-11, 20-12, 20-14, 20-18, 20-19. , .
22: 30-1, 30-2, 30-3, 30-5, 30-7, 30-8, 30-11, 30-20, 30-22, 30-29.
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23: 19-6, 20-5, 11-10, 31-9, 25-6, 45-13, 17-11, 12-8, 33-13, 22-6. , .
24: 39-27, 12-6, 21-4, 16-9, 41-12, 50-6, 32-18, 28-5, 48-14, 16-7. , .
25 , : , .
25: 2×2, 2×3, 2×4, 2×5, 2×6, 2×7, 2×8, 2×9.
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26: 3×2, 3×3, 3×4, 3×5, 3×6, 3×7, 3×8. , .
27: 4×4, 4×5, 4×6, 4×7, 4×8, 4×9. , .
28: 5×5, 5×6, 5×7, 5×8, 5×9. , .
29: 6×4, 6×5, 6×6, 6×7, 6×8. , .
30: 7×1, 7×2, 7×3, 7×4, 7×5, 7×6. , .
31: 8×1, 8×2, 8×3, 8×4, 8×5, 8×6. , .
32: 9×1, 9×2, 9×3, 9×4, 9×5. , .
33: 10×1, 10×2, 10×3, 10×4, 10×5. , .
34: 3×2, 4×3, 3×7, 10×4, 3×16, 3×6, 15×3, 5×6, 13×3, 5×4. , .