Đáp án:

Để sắp xếp được các phân số từ lớn đến bé thì ta cần tìm mẫu số chung:

Dãy 1: $\text{MSC: 24}$

$\dfrac{5}{4}$ $\text{=}$ $\dfrac{5 $\times$ 6}{4 $\times$ 6}$ $\text{=}$ $\dfrac{30}{24}$

$\dfrac{2}{3}$ $\text{=}$ $\dfrac{2 $\times$ 8}{3 $\times$ 8}$ $\text{=}$ $\dfrac{16}{24}$

$\dfrac{5}{6}$ $\text{=}$ $\dfrac{5 $\times$ 4}{6 $\times$ 4}$ $\text{=}$ $\dfrac{20}{24}$

Vậy: $\dfrac{30}{24}$ $\text{>}$ $\dfrac{20}{24}$ $\text{>}$ $\dfrac{16}{24}$ 

$\Longrightarrow$ $\dfrac{5}{4}$ $\text{>}$ $\dfrac{5}{6}$ $\text{>}$ $\dfrac{2}{3}$ 

Dãy 2: $\text{MSC: 28}$

$\dfrac{3}{2}$ $\text{=}$ $\dfrac{3 $\times$ 14}{2 $\times$ 14}$ $\text{=}$ $\dfrac{42}{28}$

$\dfrac{4}{7}$ $\text{=}$ $\dfrac{4 $\times$ 4}{7 $\times$ 4}$ $\text{=}$ $\dfrac{16}{28}$

$\dfrac{9}{14}$ $\text{=}$ $\dfrac{9 $\times$ 2}{14 $\times$ 2}$ $\text{=}$ $\dfrac{18}{28}$

Vậy: $\dfrac{42}{28}$ $\text{>}$ $\dfrac{18}{28}$ $\text{>}$ $\dfrac{16}{28}$ 

$\Longrightarrow$ $\dfrac{3}{2}$ $\text{>}$ $\dfrac{4}{7}$ $\text{>}$ $\dfrac{9}{14}$ 

`\color{yellow}{Tuancute}`