Luyện tập

6 – 4 = 2                                 

9 – 5 = 4                     

7 – 2 = 5

76 – 4 = 72                             

59 – 5 = 54                 

87 – 2 = 85

76 – 3 = 73                     

49 – 1 = 48                            

86 – 30 = 56

75 – 2 = 74                    

66 – 10 = 56

a)

50 – 10 – 30 = 10                                       

67 – 7 – 20 = 40

20 cm + 30 cm = 50 cm                                                         

70 cm – 40 cm = 30 cm

40 cm + 10 cm – 20 cm = 30 cm                                           

50 cm – 20 cm + 30 cm = 60cm