3. Вычислите: 1) 1-2,71 +1-1,31-18,21; 2) \( \frac{2}{72} : \frac{1}{12} \)

Решение:

1. \[ 1 - 2,71 - 1,31 - 18,21 = 1 - (2,71 + 1,31 + 18,21) = 1 - 22,23 = -21,23 \]
2. \[ \frac{2}{72} : \frac{1}{12} = \frac{2}{72} \times \frac{12}{1} = \frac{2 imes 12}{72 imes 1} = \frac{24}{72} = \frac{1}{3} \]

Ответ: 1) -21,23; 2) \( \frac{1}{3} \)