计算①920÷[12×（25+45）]②（0.4+23）÷（56-0.75）×0.5③1.25+114×7.4+125%÷58④393939×899899377377×939393⑤6.6-135÷（0.375×45+18×0.8）⑥514-2.125+（4.75-338）⑦1124+[（1.5-数学
=
| 9 |
| 20 |
| 3 |
| 5 |
=
| 3 |
| 4 |
②（0.4+
| 2 |
| 3 |
| 5 |
| 6 |
=
| 16 |
| 15 |
| 1 |
| 12 |
=
| 64 |
| 5 |
=6.4；
③1.25+1
| 1 |
| 4 |
| 5 |
| 8 |
=1.25+1.25×7.4+1.25×1.6，
=1.25×（1+7.4+1.6），
=1.25×10，
=12.5；
④
| 393939×899899 |
| 377377×939393 |
=
| (3×13×10101)×(29×31×1001) |
| (13×29×1001)×(3×31×10101) |
=
| 3×13××29×31×1001×10101 |
| 3×13×29×31×1001×10101 |
=1；
⑤6.6-1
| 3 |
| 5 |
| 4 |
| 5 |
| 1 |
| 8 |
=6.6-1
| 3 |
| 5 |
| 1 |
| 8 |
=6.6-1
| 3 |
| 5 |
| 1 |
| 8 |
=6.6-1
| 3 |
| 5 |
=6.6-1
| 3 |
| 5 |
=6.6-4，
=2.6；
⑥5
| 1 |
| 4 |
| 3 |
| 8 |
=5.25-2.125+4.75-3.375，
=（5.25+4.75）-（2.125+3.375），
=10-5.5，
=4.5；
⑦1
| 1 |
| 24 |
| 2 |
| 3 |
| 2 |
| 3 |
| 8 |
| 9 |
=1
