Consider the question. Mandy is 3 years old. Her brother is 4 times as old as she is. Her sister is 5 years younger than her brother. What is the age difference between Mandy and her sister?
If the answer is '4'; explain the reasoning:
Mandy's brother's age is 3 years x 4 = 12 years old. Her sister's age is 12 years - 5 years = 7 years old. The age difference between Mandy and her sister is 7 years - 3 years = 4 years.