①个位对齐
②小数点对齐
③通分
①x+0.5x=4.2
②
③(48-2x)×=7.5
①3.6﹣2.8+7.4﹣7.2
②1.25×1.6×25
③÷4
④÷[(﹣)×]
﹣2.8 +2.8
﹣﹣
÷
﹣0.99 0