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Three printers, $$X_1$$, $$X_2$$ and $$X_3$$, work only at their respective constant rates. Working together,$$X_1$$, $$X_2$$ and $$X_3$$ can complete a certain job in 9 hours; working together, $$X_2$$ and $$X_3$$ can complete the same job in 12 hours. Working alone, how many hours will it take $$X_1$$ to complete the job?
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· 相关考点
2.5.2 工作效率题
2.5.2 工作效率题
以上解析由 考满分老师提供。