Cần sự bình yên !
Bài 1.
`a) 3 . 5^2 + 15 . 2^2 - 26 : 2`
`= 3 . 25 + 15 . 4 - 13`
`= 75 + 60 - 13`
`= 135 - 13`
`= 122`
`b) {29 - [16 - 3 (51 - 49)]} + 31`
`= {29 - [16 - 3 . 2]} + 31`
`= {29 - [16 - 6]} + 31`
`= {29 - 10} + 31`
`= 19 + 31`
`= 50`
`c) 100 : 5^2 + 7 . 3^2`
`= 100 : 25 + 7 . 9`
`= 4 + 63`
`= 67`
`d) 11 + {1029 - 3 . [200 + (11 - 1)^2]}`
`= 11 + {1029 - 3 . [200 - 10^2]}`
`= 11 + {1029 - 3 . [200 - 100]}`
`= 11 + {1029 - 3 . 100}`
`= 11 + {1029 - 300}`
`= 11 + 729`
`= 740`
Bài 2.
`a) 165 : x + 12 = 15`
`165 : x = 15 - 12`
`165 : x = 3`
`x = 165 : 3`
`x = 55`
Vậy `x = 55`
`b) 5 (x - 71) + 7 = 129`
`5 (x - 71) = 129 - 7`
`5 (x - 71) = 122`
`x - 71 = 122 : 5`
`x - 71 = 122/5`
`x = 122/5 + 71`
`x = 477/5`
Vậy `x = 477/5`
Bài 3.
`a) 25 + 34 + 175 + 66`
`= (25 + 175) + (34 + 66)`
`= 200 + 100`
`= 300`
`b) 5 . 125 . 17 . 8 . 2`
`= (5 . 2) . (125 . 8) . 17`
`= 10 . 1000 . 17`
`= 10000 . 17`
`= 170000`
`c) 128 . 46 + 128 . 32 + 128 . 22`
`= 128 . (46 + 32 + 22)`
`= 128 . 100`
`= 12800`
