估算．91÷30≈ 164÷20≈ 160÷19≈80÷38≈ 633÷70≈ 810÷89≈
15.8-(6+÷12.5%)
10-÷×1
325×0.36+6.75×36
5.6×0.375+×5.4-0.375×0.9
5.6x+4x=17.28
+
÷12.5%)
-
÷
×1
×5.4-0.375×0.9
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