[
  "Let Tank B be 1 unit. Then Tank A is 4 units and Tank C is (4 units − 150).",
  "Total units: 1 + 4 + 4 = 9 units. Then 9 units − 150 = 1350.",
  "Solve: 9 units = 1500, so 1 unit = 1500 ÷ 9 = 166 2/3 litres."
]