[
  "Convert the mixed number to an improper fraction, then multiply by the whole number. Finally simplify the result to its simplest form.",
  "3 2/9 = 29/9. Then 29/9 x 21 = (29 x 21)/9 = 609/9. Divide: 609 / 9 = 67 remainder 6, so 67 6/9 = 67 2/3.",
  "3 2/9 x 21 = 67 2/3. Answer: 67 2/3 (option A)."
]