Ответ:

  1. \(30\,999 + 1 = 31\,000\).
  2. \(10\,000 - 1 = 9\,999\).
  3. \(25\,909 + 1 = 25\,910\).
  4. \(100\,000 - 1 = 99\,999\).
  5. \(39\,099 + 1 = 39\,100\).
  6. \(40\,000 - 1 = 39\,999\).
  7. \(699\,999 + 1 = 700\,000\).