脱式计算．能简便计算的用简便方法计算．①137×45+247×45+45②（27+15）×7×5③12-27+17÷15④89×[34-（716-14）]．-数学
=（4+1）×
| 4 |
| 5 |
=5×
| 4 |
| 5 |
=4；
②（
| 2 |
| 7 |
| 1 |
| 5 |
=（
| 2 |
| 7 |
| 1 |
| 5 |
=
| 2 |
| 7 |
| 1 |
| 5 |
=
| 2 |
| 7 |
| 1 |
| 5 |
=2×5+1×7，
=10+7，
=17；
③12-
| 2 |
| 7 |
| 1 |
| 7 |
| 1 |
| 5 |
=12-
| 2 |
| 7 |
| 5 |
| 7 |
=12+（
| 5 |
| 7 |
| 2 |
| 7 |
=12+
| 3 |
| 7 |
=12
| 3 |
| 7 |
④
| 8 |
| 9 |
| 3 |
| 4 |
| 7 |
| 16 |
| 1 |
| 4 |
=
| 8 |
| 9 |
