(15-4.5)/0.5=10.5/0.5=21 (15-4.5)÷0.5=15÷0.5-4.5÷0.5=30-9=21
(15-4.5)÷0.5=15÷0.5-4.5÷0.5=30-3=27
.原式=(15--4.5)x 2 =15x2--4.5x2 =30--9 =21
=15÷0.5-4.5÷0.5=30-13=17
(15-4.5)*2=21