`2/5``=` $\frac{2×4}{5×4}$ `=` $\frac{8}{20}$ 

$\frac{3}{4}$ `=` $\frac{3×5}{4×5}$ `=`$\frac{15}{20}$ 

Ta rút gọn`:`

$\frac{8}{20}$ `=` $\frac{2}{5}$

 $\frac{15}{20}$ `=` $\frac{3}{4}$

Vậy`:`

$\frac{2}{5}$ `<` $\frac{3}{4}$ `2/3`