`1) 240 : ( x - 57) = 12`
`( x - 57) = 240 : 12`
`x - 57 = 20`
`x = 20 + 57`
`x = 77`
Vậy `x = 77`
``
`2) ( x - 27) : 12 = 18`
`( x - 27) = 18 xx 12`
`x - 27 = 216`
`x =216 + 27`
`x = 243`
Vậy `x = 243`
``
`3) 26 + 18 xx x = 16 xx x + 146`
`18 xx x - 16 xx x = 146 - 26`
`( 18 - 16) xx x = 120`
`2 xx x = 120`
`x = 120 : 2`
`x = 60`
Vậy `x = 60`
``
`4) 3600 : [ ( 5 xx x + 335) : x] = 50`
` [ ( 5 xx x + 335) : x] = 3600 : 50`
`( 5 xx x + 335) : x = 72`
`5 xx x : x + 335 : x = 72`
`5 + 335 : x = 72`
`335 : x = 72 - 5`
`335 : x = 67`
`x = 335 : 67`
`x = 5`
Vậy `x = 5`
``
`5) x/5 = 5/6 - 1/2`
`x/5 = 1/3`
⇒ `x xx 3 = 5 . 1`
`x xx 3 = 5`
`x = 5 : 3`
`x = 5/3`
``
`6) 5/6 - x = 3/4 - 1/3`
`5/6 - x = 5/12`
`x = 5/6 - 5/12`
`x= 5/12`
``
`7) 9/15 xx ( x - 2) = 3/7`
`( x - 2) = 3/7 : 9/15`
`x - 2 = 2/3`
`x = 2/3 + 2`
`x = 8/3`
Vậy `x = 8/3`
``
`8) 2 3/5 x + 3 1/3 = 8 2/3`
`2 3/5 x = 8 2/3 - 3 1/3`
`2 3/5 x = 5 1/3`
`x = 5 1/3 : 2 3/5`
`x = 2 2/39`
`x = 80/39`
Vậy `x = 80/39`
``
`9) x : ( 3/14 - 1/7) = 4 3/8`
`x : 1/14 = 4 3/8`
`x = 4 3/8 xx 1/14`
`x= 5/16`
Vậy `x = 5/16`
