=8.7/（2.9*6）=87/29/6=87/6/29=87/3/2/29=29/2/29=29/29/2=0.5
8.7÷（2.9×6）＝8.7÷2.9÷6＝3÷6＝0.5
8.7÷(2.9×6)＝(2.9×3)÷(2.9×6)＝3÷6＝0.5
