①5.6+1.79+4.4+8.21
②14.53-(4.53+8.7)
③7600÷25÷4
④17×62-62×7
⑤83×99+83
⑥120+880÷40+60
⑦900÷5×(48-30)
⑧900÷[5×(48-30)]