[
  "Let School B have x students. School A has x + 200.",
  "Set up: 0.75(x + 200) + 0.60x = 630. Simplify to 1.35x + 150 = 630.",
  "Solve: x = 480/1.35 = 3200/9 for School B. School A = 5000/9."
]