一个数是78，另一个数是39，它们的差是多少？
①+=②+=③﹣= ④2﹣=⑤+=⑥+=
下面各题怎样算简便就怎样算． 6﹣﹣．
直接写得数．﹣=﹣=+=+=+=﹣=﹣= 0.3+=
脱式计算，能简算的要简算+++﹣﹣．
直接写得数 += 1÷=×12×=×+×=+++= 8﹣= 2.25﹣0.25=×÷=÷﹣×= 5﹣﹣=
+
+
=③
﹣
=
=⑤
+
=⑥
+
=
﹣
．
﹣
=
﹣
=
+
=
+
=
+
=
﹣
=
﹣
= 0.3+
+
+
+
﹣
﹣
．
+
= 1÷
=
×12×
=
×
+
×
=
+
+
+
=
= 2.25﹣0.25=
×
÷
=
÷
﹣
×
= 5﹣
﹣
=
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