1.  看谁算得快。                                                                                                                                      

6＋2＝	9－6＝	1＋3＋2＝	10－4－4＝
5＋5＝	10－3＝	0＋1＋9＝	9－4－3＝
2＋7＝	8－7＝	9－3－3＝	3＋7－5＝