[
  "Add the two amounts by converting both mixed numbers to improper fractions with a common denominator. LCM of 3 and 9 is 9.",
  "3 1/3 = 10/3 = 30/9. 3 7/9 = 34/9. 30/9 + 34/9 = 64/9.",
  "64/9 = 7 1/9 kg. Answer: 7 1/9 (option D)."
]