直接写得数。                                                                                                                                       

400﹣80＝	70+140＝	900+800＝	100﹣40＝
760+120＝	980﹣460＝	650﹣30＝	300+3000＝
400+198≈	701﹣195≈	3003﹣2007≈	94+495≈