Đáp án:
1.
`(-38) + |-12| . 4`
`= -38 + 12 . 4`
`= -38 + 48`
`= 10`
`621 - {[(117 + 3) : 5] - 3^2}`
`= 621 - {[120 : 5] - 9}`
`= 621 - {24 - 9}`
`= 621 - 15`
`= 606`
2.
`a) 96 - 3 . (x + 1) = 42`
`3 . (x + 1) = 96 - 42`
`3 . (x + 1) = 54`
`x + 1 = 54 : 3`
`x + 1 = 18`
`x = 18 - 1`
`x = 17`
Vậy `x = 17`
`b) 15x - 9x + 2x = 72`
`(15 - 9 + 2) . x = 72`
`8 . x = 72`
`x = 72 : 8`
`x = 9`
Vậy `x = 9`
`c) 75:x=(-10)+(-5)+30`
`75 : x = (-15) + 30`
`75 : x= 15`
`x = 75 : 15`
`x = 5`
Vậy `x = 5`
`d) (7x-24) . 5^4 = 5^6`
`(7x - 24) = 5^6 : 5^4`
`7x - 24 = 5^2`
`7x - 24 = 25`
`7x = 25 + 24`
`7x = 49`
`x = 49 : 7`
`x = 7`
Vậy `x = 7`
