Ответ:

  1. \(800-3\cdot40+120=800-120+120=800\).

  2. \(700+60:3-150=700+20-150=570\).

  3. \(900-5\cdot4+80=900-20+80=960\).

  4. \(150-80:4\cdot5+30=150-20\cdot5+30=150-100+30=80\).

  5. \(250-40\cdot5-20=250-200-20=30\).

  6. \(120-54:9\cdot5+48=120-6\cdot5+48=120-30+48=138\).