问题标题:
【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.
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