你认为怎样算简便就怎样算．
24.6+31.79+25.4             3.21﹣1．O5﹣1.7               （0.5+0.25）×4
76﹣2.4÷0.08               4÷[1﹣（0.8+0.12）]            2.46×9+9×7.54