question: Wendy is five times as old as Colin will be seven years from now. In 25 years, Colin will be a third as old as Wendy is now. How old is Colin now?
answer: Let x be Colin's age now.
  (x+7)*5=(x+25)*3
  5*x+35=3*x+75
  2*x=40
  x=<<20=20>>20
  #### 20