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   问题:

【一道英文数学提!janetisthreetimesasoldasherdaughter,mary.fiveyearsagojantwasfourtimesjanetisthreetimesasoldasherdaughter,mary.fiveyearsagojantwasfourtimesasoldasmary.howoldisjanetnow?howoldwillmarybein】

问题描述:

一道英文数学提!janetisthreetimesasoldasherdaughter,mary.fiveyearsagojantwasfourtimes

janetisthreetimesasoldasherdaughter,mary.fiveyearsagojantwasfourtimesasoldasmary.howoldisjanetnow?howoldwillmarybein7years'time

李良炎回答:

  SupposeMaryisxyearsoldnow.Then

  4*(x-5)=3x-5

  Solveit,getx=15

  SoJanetis3x=45yearsoldnowandMarywillbe22yearsoldin7years'time.