\[\begin{array}{l}
\frac{2}{3};\frac{3}{5}\\
M{\rm{S}}C = 15\\
\frac{2}{3} = \frac{{2 \times 5}}{{3 \times 5}} = \frac{{10}}{{15}}\\
\frac{3}{5} = \frac{{3 \times 3}}{{5 \times 3}} = \frac{9}{{15}}\\
\frac{7}{4};\frac{9}{5}\\
M{\rm{S}}C = 20\\
\frac{7}{4} = \frac{{7 \times 5}}{{4 \times 5}} = \frac{{35}}{{20}}\\
\frac{9}{5} = \frac{{9 \times 4}}{{5 \times 4}} = \frac{{36}}{{20}}\\
\frac{3}{8};\frac{{13}}{5}\\
M{\rm{S}}C = 40\\
\frac{3}{8} = \frac{{3 \times 5}}{{8 \times 5}} = \frac{{15}}{{40}}\\
\frac{{13}}{5} = \frac{{13 \times 8}}{{5 \times 8}} = \frac{{104}}{{40}}\\
\frac{2}{9};\frac{{10}}{4}\\
M{\rm{S}}C = 36\\
\frac{2}{9} = \frac{{2 \times 4}}{{9 \times 4}} = \frac{8}{{36}}\\
\frac{{10}}{4} = \frac{{10 \times 9}}{{4 \times 9}} = \frac{{90}}{{36}}
\end{array}\]

2/3 = 10/15 và 3/5 = 9/15

7/4 = 35/20 và 9/5 = 36/20

3/8 = 15/40 và 13/5 = 104/40

2/9 = 8/36 và 90/36