[
  "Draw a bar model: Mathematics = 9 units, Science = 5 units. Mathematics is 90 marks, so 9 units = 90.",
  "1 unit = 90 / 9 = 10 marks. Science = 5 x 10 = 50 marks. Difference = 90 - 50 = 40.",
  "He scored 40 more marks for Mathematics than Science."
]