Cách làm cho bạn:
$\frac{5}{3} + \frac{4}{7}= \frac{35}{21}+\frac{12}{21} =\frac{47}{21}$
$\frac{2}{3} - \frac{3}{9}=\frac{6}{9}-\frac{3}{9}=\frac{3}{9}=\frac{1}{3}$
$\frac{2}{5}\times \frac{8}{11}=\frac{2\times 8}{5\times 11}=\frac{16}{88}=\frac{5}{44}$
$\frac{3}{7}:\frac{5}{14}=\frac{6}{14}\times \frac{14}{5}=\frac{6}{5}$
$\frac{3}{8}+\frac{6}{15}:\frac{3}{5} =\frac{3}{8}+\frac{6}{15}\times \frac{5}{3}=\frac{3}{8}+\frac{30}{45}=\frac{135}{360}+\frac{240}{360}=\frac{375}{360}$
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