对的画“√”,错的画“×”并改正...

45+55÷5-20      

=100÷5-20                     

=20-20           改正：      

=0   (  )                     

12×(280-80÷4)

=12×(200÷4)     改正：

=12×50

=600   (  )

【答案】×

45+55÷5-20      

=45+11-20                     

=56-20               

=36

× 

12×(280-80÷4)

=12×(280-20)  

=12×260

=3120

【解析】

略