Tính giá trị biểu thức.

 a) 55 : 5 × 7     

= 11 × 7   

= 77                                                                                           

b) 70 : 5 : 7   

= 14 : 7      

= 2                                                                                            

c) 24 × 3 : 8

= 72 : 8

= 9