[
  "Set pie = 1 unit. Then a cake = 1 unit + $2.50.",
  "Total items: 9 cakes give 9 extra $2.50 amounts = $22.50 in extras. Remaining value ($72 - $22.50 = $49.50) covers 22 units.",
  "1 unit = $49.50 ÷ 22 = $2.25 (pie). Cake = $2.25 + $2.50 = $4.75."
]