Выполняем деление:

1. a) $$rac{3n}{4m} : \frac{27n^4}{16} = \frac{3n}{4m} \times \frac{16}{27n^4} = \frac{3 \times 16 \times n}{4 \times 27 \times m \times n^4} = \frac{4 \times 1}{1 \times 9 \times m \times n^3} = \frac{4}{9mn^3}$$
2. б) $$rac{36a^5}{11b} : (12a^3b^2) = \frac{36a^5}{11b} \times \frac{1}{12a^3b^2} = \frac{36a^5}{11 \times 12a^3b^3} = \frac{3a^2}{11b^3}$$
3. в) $$26x^7 : \frac{39x^4}{5y} = 26x^7 \times \frac{5y}{39x^4} = \frac{26x^7 \times 5y}{39x^4} = \frac{2x^3 \times 5y}{3} = \frac{10x^3y}{3}$$
4. г) $$\frac{15xy}{7ab} : (\frac{10x^4y}{21a^3b^2}) = \frac{15xy}{7ab} \times \frac{21a^3b^2}{10x^4y} = \frac{15xy \times 21a^3b^2}{7ab \times 10x^4y} = \frac{3 \times 3a^2b}{1 \times 2x^3} = \frac{9a^2b}{2x^3}$$