[
  "Last week total = $8 + $6 = $14.",
  "This week: sandwich = $8 * 1.25 = $10, juice = $6 * 1.50 = $9. New total = $19.",
  "Percentage increase = (19 - 14) / 14 * 100% = 5/14 * 100% = 35 5/7 %."
]