12) 4 1/12 * 8 6/7 * 7 2/3 * 5 1/7 * 7 / 6 1/4 * 1 2/5 * 5 3/4 * 3 4/9 * 7 1/5

12) $\frac{49/12 \cdot 62/7 \cdot 23/3 \cdot 36/7 \cdot 7}{25/4 \cdot 7/5 \cdot 23/4 \cdot 31/9 \cdot 36/5} = \frac{(49 \cdot 62 \cdot 23 \cdot 36 \cdot 7) / (12 \cdot 7 \cdot 3 \cdot 7)}{(25 \cdot 7 \cdot 23 \cdot 31 \cdot 36) / (4 \cdot 5 \cdot 4 \cdot 9 \cdot 5)} = \frac{49 \cdot 62 \cdot 36 \cdot 23 / (12 \cdot 3)}{25 \cdot 7 \cdot 23 \cdot 31 \cdot 36 / (4 \cdot 5 \cdot 4 \cdot 9 \cdot 5)} = \frac{49 \cdot 62 \cdot 3}{25 \cdot 31 / 16} = \frac{9114}{12.109375} \approx 752.6$ (результат упрощения дробей) 13) $(15 : 5/18 : 27/8) \cdot (1/16 + 11/36 + 5/48 + 5/18) = (15 \cdot 18/5 \cdot 8/27) \cdot (9/144 + 44/144 + 15/144 + 40/144) = (54 \cdot 8/27) \cdot 108/144 = 16 \cdot 0.75 = 12$ Знаменатель: $(11 5/14 - 8 21/22) : 1 2/3 = (159/14 - 197/22) : 5/3 = ((1749-1379)/154) : 5/3 = 370/154 \cdot 3/5 = 185/77 \cdot 3/5 = 111/77 \approx 1.44$. Ответ: $12 / (111/77) = 924/111 \approx 8.32$ 14) Числитель: $(33/54 + 11/16) \cdot (14/15 - 7/12) \cdot 16/7 \cdot 8/9 : 109/27 = (11/18 + 11/16) \cdot (56/60 - 35/60) \dots = (88+99)/144 \cdot 21/60 \dots = 187/144 \cdot 7/20 \cdot 16/7 \cdot 8/9 \cdot 27/109 = 187/144 \cdot 16/20 \cdot 8/9 \cdot 27/109 = 187/144 \cdot 4/5 \cdot 8/9 \cdot 27/109 = 187 \cdot 8 / (18 \cdot 5 \cdot 109) = 1496 / 9810 \approx 0.15$ 15) $1.24 : 3.1 + 12 : 0.25 - 2 : 25 + 18 : 0.45 = 0.4 + 48 - 0.08 + 40 = 88.32$ 16) $(1.87 + 1.955) : 0.85 - (3 \cdot 1.75 - 2.5) \cdot 1.62 = 3.825 : 0.85 - (5.25 - 2.5) \cdot 1.62 = 4.5 - 2.75 \cdot 1.62 = 4.5 - 4.455 = 0.045$ 17) $(1.5 : 1/3 - 3/8 : 0.25) \cdot 3.2 - 3.2 \cdot 5/8 = (4.5 - 1.5) \cdot 3.2 - 3.2 \cdot 0.625 = 3 \cdot 3.2 - 2 = 9.6 - 2 = 7.6$ 18) $4.5 + 0.5 \cdot (2.4 \cdot 1.375 - 1.64 : 0.8) : 25/12 - 9/7 \cdot 14 = 4.5 + 0.5 \cdot (3.3 - 2.05) : 25/12 - 18 = 4.5 + 0.5 \cdot 1.25 \cdot 12/25 - 18 = 4.5 + 0.3 - 18 = -13.2$ 19) $(2.314 - 0.25) : 0.02 + (1.6875 + 0.7125) : 3 = 2.064 : 0.02 + 2.4 : 3 = 103.2 + 0.8 = 104$ 20) $(3.625 + 0.25 + 2.75) : (28.75 + 92.25 - 15) : 0.0625 = 6.625 : 106 : 0.0625 = 0.0625 : 0.0625 = 1$