[
  "Since the number of boys who passed equals the number of girls who passed, and total passed = 240, each group had 120 pass.",
  "Boys pass rate is 75%: 0.75 * b = 120, so b = 160.",
  "Girls: 80% pass (since 20% fail): 0.80 * g = 120, so g = 150. Total = 310."
]