question: Martha has been collecting shells since she turned 5 years old, every month she collects one shell. By her 10th birthday, how many shells will Martha have collected?
answer: In 12 months of the year, Martha collects 12 * 1 = <<12*1=12>>12 shells.
  From her 5th to her 10th birthday, 10 - 5 = <<10-5=5>>5 years have passed.
  During the 5 years that have passed, Martha has collected 12 * 5 = <<12*5=60>>60 shells.
  #### 60