在商场里甲开始乘自动扶梯从一楼到二楼，并在上向上走，同时乙站在速度相等的并排扶梯从二层到一层。当甲乙处于同一高度时，甲反身向下走，结果他一共走了60级，如果他一直走到顶端再反身向下走，则一共要走80级，那么，自动扶梯不动时从下到上要走多少级？
直接写出得数．========
口算． 4.2÷=×3=÷5=（+）×72=×12=×1.8=÷=
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直接写出得出． 20×=÷=×=+=÷6=×12=+= 6÷=﹣=×=×= 0÷=
直接写出得数． 6×=÷7=÷= 4×1=×=÷=÷5= 5×=﹣=+0.5= 1÷1= 1÷1=
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=
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=
=
=
=
=
×3=
÷5=（
+
）×72=
×12=
÷
=
=
=
=
=
=
=
=
=
÷
=
×
=
+
=
÷6=
+
= 6÷
=
﹣
=
×
=
×
= 0÷
=
=
÷7=
÷
= 4×1
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×
=
÷
=
÷5= 5×
=
﹣
=
+0.5= 1
÷1= 1÷1
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