Theo đề, ta có:
\(\left\{{}\begin{matrix}\dfrac{1}{x}+\dfrac{1}{y}=\dfrac{3}{10}\\\dfrac{3}{x}+\dfrac{2}{y}=\dfrac{4}{5}\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}\dfrac{3}{x}+\dfrac{3}{y}=\dfrac{9}{10}\\\dfrac{3}{x}+\dfrac{2}{y}=\dfrac{4}{5}\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}\dfrac{1}{y}=\dfrac{1}{10}\\\dfrac{1}{x}+\dfrac{1}{y}=\dfrac{3}{10}\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=10\\x=5\end{matrix}\right.\)
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