question: Juan and his brother Carlos are selling lemonade. For each gallon they make it costs $3 for lemons and $2 for sugar. They sell each glass for $0.50 and get 20 glasses per gallon. If they made $25 in profit, how much did they spend on lemons?
answer: Each gallon sells for a total of $10 because 20 x .5 = <<20*.5=10>>10
  Each gallon costs $5 to make because 3 + 2 = <<5=5>>5
  They make $5 off each gallon because 10 - 5 = <<10-5=5>>5
  They made and sold 5 gallons because 25 / 5 = <<25/5=5>>5
  They spent $15 on lemons because 5 x 3 = <<5*3=15>>15
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