[
  "Draw a bar model: The age gap never changes. Gap = 30 - 18 = 12 years.",
  "When Max was half his brother's age: Max = 1 unit, Brother = 2 units. Gap = 1 unit = 12. Max was 12 years old.",
  "Years ago = 18 - 12 = 6. Answer: 6 years ago."
]