[
  "Draw a bar model: the total amount of money stays the same before and after the transfer.",
  "At first: Dave = 2u, Brother = 3u. After: Dave = 2u - 10, Brother = 3u + 10. Ratio is 1 : 2, so 2(2u - 10) = 1(3u + 10). Solve: 4u - 20 = 3u + 10, u = 30.",
  "Dave had 2 x 30 = $60, his brother had 3 x 30 = $90."
]