①15.3÷3 -(45.6-42.6)
②8×0.4×1.25×5
③(5.6+7.8)×(9.6-2.4)
④12+[5.5×(3.1-2.7)]
⑤2.5×3.7×4
⑥3.2×102
⑦8.9×6-3.9×6