{
  "question_id": 5110,
  "hints": [
    {
      "hint_level": 1,
      "hint": "Sister's age = v + 4."
    },
    {
      "hint_level": 2,
      "hint": "Substitute v = 9."
    },
    {
      "hint_level": 3,
      "hint": "9 + 4 = 13 years old."
    }
  ]
}