226. Сократите: 1) 12 * 21 / 35 * 15; 2) 72 * 11 / 33 * 30; 3) 25 * 17 * 44 / 51 * 8 * 75; 4) 8 * 3 + 8 * 23 / 3 * 16; 5) 17 * 48 / 17 * 16 - 9 * 16; 6) 14 * 5 - 14 * 3 / 21 * 9 + 21 * 3

1) $\frac{12 \cdot 21}{35 \cdot 15} = \frac{(3 \cdot 4) \cdot (7 \cdot 3)}{(5 \cdot 7) \cdot (3 \cdot 5)} = \frac{12 \cdot 21}{35 \cdot 15} = \frac{\cancel{12}^4 \cdot \cancel{21}^3}{\cancel{35}_5 \cdot \cancel{15}_5} = \frac{4 \cdot 3}{5 \cdot 5} = \frac{12}{25}$ 2) $\frac{72 \cdot 11}{33 \cdot 30} = \frac{72 \cdot 11}{33 \cdot 30} = \frac{\cancel{72}_{12} \cdot \cancel{11}^1}{\cancel{33}_3 \cdot \cancel{30}_5} = \frac{12 \cdot 1}{3 \cdot 5} = \frac{12}{15} = \frac{4}{5}$ 3) $\frac{25 \cdot 17 \cdot 44}{51 \cdot 8 \cdot 75} = \frac{25 \cdot 17 \cdot 44}{51 \cdot 8 \cdot 75} = \frac{\cancel{25}^1 \cdot \cancel{17}^1 \cdot \cancel{44}^{11}}{\cancel{51}_3 \cdot \cancel{8}_2 \cdot \cancel{75}_3} = \frac{11}{3 \cdot 2 \cdot 3} = \frac{11}{18}$ 4) $\frac{8 \cdot 3 + 8 \cdot 23}{3 \cdot 16} = \frac{8 \cdot (3 + 23)}{3 \cdot 16} = \frac{8 \cdot 26}{3 \cdot 16} = \frac{\cancel{8}^1 \cdot 26}{3 \cdot \cancel{16}_2} = \frac{26}{3 \cdot 2} = \frac{26}{6} = \frac{13}{3} = 4\frac{1}{3}$ 5) $\frac{17 \cdot 48}{17 \cdot 16 - 9 \cdot 16} = \frac{17 \cdot 48}{16 \cdot (17 - 9)} = \frac{17 \cdot 48}{16 \cdot 8} = \frac{17 \cdot \cancel{48}^6}{16 \cdot 8} = \frac{17 \cdot 6}{16} = \frac{17 \cdot 3}{8} = \frac{51}{8} = 6\frac{3}{8}$ 6) $\frac{14 \cdot 5 - 14 \cdot 3}{21 \cdot 9 + 21 \cdot 3} = \frac{14 \cdot (5 - 3)}{21 \cdot (9 + 3)} = \frac{14 \cdot 2}{21 \cdot 12} = \frac{\cancel{14}^2 \cdot 2}{\cancel{21}_3 \cdot 12} = \frac{2 \cdot 2}{3 \cdot 12} = \frac{4}{36} = \frac{1}{9}$