Ответ:

  1. \(8\,000 : 10 \cdot 100 = 800 \cdot 100 = 80\,000\).
  2. \(90 \cdot 1\,000 : 100 = 90\,000 : 100 = 900\).
  3. \(530\,000 : 1\,000 + 70 = 530 + 70 = 600\).
  4. \(36 \cdot 100 - 600 = 3\,600 - 600 = 3\,000\).