Running at their respective constant rates, Machine X takes 2 days longer to produce w widgets than Machine Y. At these rates, if the two machines together produce ~$5 \over 4$~ w widgets in 3 days, how many days would it take Machine X alone to produce 2W widgets?
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列方程太烦了,直接套答案进x/1+(x-2)/1=5/12比较快。然而我算出来x=6后直接选了6错掉了T_T
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