Tính. 92 – 47 + 11 = 

92 – 47 + 11 = 45 + 11

              = 56

66 – 6 + 30 = 60 + 30

               = 90

56 + 39  – 38 = 95 – 38

               = 57 

54 – 36 + 21 = 18 + 21 

               = 39