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. \(90\,100-1=90\,099\).

  6. \(40\,000-1=39\,999\).

  7. \(39\,099+1=39\,100\).

  8. \(699\,999+1=700\,000\).

Ответ: 31 000; 9 999; 25 910; 99 999; 90 099; 39 999; 39 100; 700 000.