用递等式计算115﹣15×6 54×（31﹣16） 420÷14×21 83﹣39+41．
直接写得数=====
直接写出得数． 17×=+=×52= 1÷= 3﹣=÷3= 0.32= 20×5.5=
直接写出得数+=﹣=÷= 0.37+1.6=
+=÷= 12.6﹣6.06= 201+75=×=
直接写出得数：﹣= 6×= 0÷=×=+=÷=×=×=
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=
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+
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×52= 1÷
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÷3= 0.32= 20×5.5=
+
=
﹣
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÷
= 0.37+1.6=
+
=
÷
= 12.6﹣6.06= 201+75=
×
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﹣
= 6×
= 0÷
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×
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+
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÷
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×
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×
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