a与b是两个两位数,它们的和为45,将a放在b的左边,组成一个4位数,则这个4位数恰好为a与b之差的504倍,a=?

a与b是两个两位数,它们的和为45,将a放在b的左边,组成一个4位数,则这个4位数恰好为a与b之差的504倍,a=?A.18 B.20 C.25 D.28

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一个分数,分母减少了原来的1/3,分子变为原先的5/3,则所得分数是原分数值的(  )

一个分数,分母减少了原来的1/3,分子变为原先的5/3,则所得分数是原分数值的(  )A.2.5倍 B.3倍 C.5倍 D.1/3

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The word "they" in sentence 4, Para.2 refers to __________.

The word "they" in sentence 4, Para.2 refers to __________.A.older people B.new

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Police are __________ the disappearance of two children.

Police are __________ the disappearance of two children.

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__________ Tom has done really amazed everyone in his class.

__________ Tom has done really amazed everyone in his class.

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