Đáp án+Giải thích các bước giải:
`a, 200 - 8(2x + 7) = 112`
` 8(2x + 7) = 200 - 112`
` 8(2x + 7) = 88`
` 2x + 7 = 88 : 8`
` 2x + 7 = 11`
` 2x = 11 - 7`
` 2x = 4`
` x = 4 : 2`
` x = 2`
`Vậy x = 2`
`b, 415 - 9 . (x + 2) = 2^2 . 5^2`
` 415 - 9 . (x + 2) = 4 . 25`
` 415 - 9 . (x + 2) = 100`
` 9 . (x + 2) = 415 - 100`
` 9 . (x + 2) = 315`
` x + 2 = 315 : 9`
` x + 2 = 35`
` x = 35 - 2`
` x = 33`
`Vậy x = 33`
`e, 1890 : [63 - (3x + 15)] = 21 . 5`
` 1890 : [63 - (3x + 15)] = 105`
` 63 - (3x + 15) = 1890 : 105`
` 63 - (3x + 15) = 18`
` 3x + 15 = 63 - 18`
` 3x + 15 = 45`
` 3x = 45 - 15`
` 3x = 30`
` x = 30 : 3`
` x = 10`
`Vậy x = 10`
`f, 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`
