question: Kris is trying to earn a video game achievement for playing a total of 30 hours. If Kris plays for half an hour every day for 2 weeks then plays for 2 hours every day for a week, how many hours does she still need to play to earn the achievement?
answer: Two weeks is the same as 2 weeks * 7 days = <<2*7=14>>14 days.
  So playing for half an hour every day means Kris will have played for 0.5 hours * 14 days = <<0.5*14=7>>7 hours.
  Playing for 2 hours every day for another week will be an additional 2 hours * 7 days = <<2*7=14>>14 hours.
  She therefore still needs to play 30 – 7 – 14 = <<30-7-14=9>>9 hours.
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