Решим пример по действиям:
1) $$47 \frac{1}{5} = \frac{47 \cdot 5 + 1}{5} = \frac{236}{5}$$
2) $$\frac{236}{5} : 12 = \frac{236}{5} : \frac{12}{1} = \frac{236}{5} \cdot \frac{1}{12} = \frac{236}{60} = \frac{59}{15}$$
3) $$6 \frac{3}{7} = \frac{6 \cdot 7 + 3}{7} = \frac{45}{7}$$
4) $$20 : \frac{45}{7} = 20 \cdot \frac{7}{45} = \frac{140}{45} = \frac{28}{9}$$
5) $$\frac{59}{15} - \frac{28}{9} = \frac{59 \cdot 3 - 28 \cdot 5}{45} = \frac{177 - 140}{45} = \frac{37}{45}$$
6) $$10 \cdot \frac{37}{45} = \frac{370}{45} = \frac{74}{9}$$
7) $$1 \frac{35}{36} = \frac{1 \cdot 36 + 35}{36} = \frac{71}{36}$$
8) $$\frac{74}{9} - \frac{71}{36} = \frac{74 \cdot 4 - 71}{36} = \frac{296 - 71}{36} = \frac{225}{36} = \frac{25}{4}$$
9) $$1 \frac{13}{15} = \frac{1 \cdot 15 + 13}{15} = \frac{28}{15}$$
10) Приведем дроби в скобках к общему знаменателю. Общий знаменатель для 42, 56 и 48 это 336:
$$\frac{31}{42} + \frac{47}{56} + \frac{25}{48} = \frac{31 \cdot 8 + 47 \cdot 6 + 25 \cdot 7}{336} = \frac{248 + 282 + 175}{336} = \frac{705}{336} = \frac{235}{112}$$
11) $$ \frac{28}{15} \cdot \frac{235}{112} = \frac{28 \cdot 235}{15 \cdot 112} = \frac{1 \cdot 47}{3 \cdot 4} = \frac{47}{12}$$
12) $$6 - \frac{47}{12} = \frac{6 \cdot 12 - 47}{12} = \frac{72 - 47}{12} = \frac{25}{12}$$
13) $$\frac{25}{4} : \frac{25}{12} = \frac{25}{4} \cdot \frac{12}{25} = \frac{1}{1} \cdot \frac{3}{1} = 3$$
Ответ: 3