`a) x + 5x - 18 = 24`
`x ( 5 + 1) = 24 + 18`
`x . 6 = 42`
`x = 42 : 6`
`x =7`
`Vậy` `x = 7`
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`b) 8x - x = 77`
`(8 -1) x = 77`
`7x = 77`
`x = 77 : 7`
`x = 11`
`Vậy` `x = 11`
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`c)2x - 138 = 72`
`2x = 72 + 138`
`2x = 210`
`x = 210 : 2`
`x =105`
`Vậy` `x = 105`
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`d) 7x + x = 24`
`(7+1) x = 24`
`8x = 24`
`x = 24 : 8`
`x = 3`
`Vậy` `x = 3`
