question: Alice is 7 years older than Beth, who is 5 years older than Erica. What is the difference between the ages of Alice and Erica, if Erica is 30 years old?
answer: Beth is 30+5 = <<30+5=35>>35 years old.
  Alice is 35+7 = <<35+7=42>>42 years old.
  The difference between the ages of Alice and Erica is 42-30 = <<42-30=12>>12 years.
  #### 12