Задание 4

1. a) $$5 \frac{1}{12} \div 4 = \frac{5 \times 12 + 1}{12} \div 4 = \frac{61}{12} \div 4 = \frac{61}{12} \times \frac{1}{4} = \frac{61}{48} = 1 \frac{13}{48}$$

   Ответ: $$1 \frac{13}{48}$$

2. b) $$7 \frac{2}{10} \div \frac{2}{5} = \frac{7 \times 10 + 2}{10} \div \frac{2}{5} = \frac{72}{10} \div \frac{2}{5} = \frac{72}{10} \times \frac{5}{2} = \frac{72 \times 5}{10 \times 2} = \frac{72 \times 5}{2 \times 5 \times 2} = \frac{72}{2 \times 2} = \frac{72}{4} = 18$$

   Ответ: $$18$$