question: John brings his dog to the vet. His dog needs 2 vaccines, which are $20 each, and a heartworm check. The heartworm check is 60% of his total bill. If he brought $125 with him, how much does he leave with?
answer: The vaccines cost 40 because 2 x 20 = <<2*20=40>>40
  The vaccines are 40% of his total bill because 100 - 60 = <<100-60=40>>40
  The total bill is $100 because 40 / .4 = <<40/.4=100>>100
  He leaves with $25 because 125 - 100 = <<125-100=25>>25
  #### 25