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720÷(15-3×2)=720÷(12×2)=720÷24=30(判断对错)改正.3889-(108+31)×5=3889-149×5=3889-745=3144(判断对错)改正.(800+200÷50)×3=(100÷50)×3=20×3=60

题目详情
720÷(15-3×2)
=720÷(12×2)
=720÷24         
=30     
______(判断对错)
改正______.

3889-(108+31)×5
=3889-149×5     
=3889-745        
=3144
______(判断对错)
改正______.


(800+200÷50)×3
=(100÷50)×3
=20×3
=60     
______(判断对错)
改正______.
▼优质解答
答案和解析
(1)×;
改正:720÷(15-3×2)
=720÷(15-6)
=720÷9
=80;

(2)×;
改正:3889-(108+31)×5
=3889-139×5
=3889-695
=3194;

(3)×;
改正:(800+200÷50)×3
=(800+4)×3
=804×3
=2412.