①100-870÷29-88
=100-30-88
=-18
②15÷7.5+4.6-6.6
=2+4.6-6.6
=6.6-6.6
=0
③3.5×64×12.5
=(3.5×8)×(8×12.5)
=28×100
=2800
④51×7.5-49×7.5-1
=(51-49)×7.5-1
=2×7.5-1
=15-1
=14
⑤4×(4.8+3.2÷4-5.6)
=4×(4.8+0.8-5.6)
=4×0
=0
⑥[8+(5-2)÷1.2]×5
=[8+3÷1.2]×5
=10.5×5
=52.5