`x + 5/3 = y - 4/5 = z + 1/7`
`3x -2y -4z =54` $(*)$
` x + 5/3 = y - 4/5 => y = x +5/3 + 4/5 = x+ 37/15` `(1)`
` x + 5/3 = z + 1/7 => z = x+ 5/3 - 1/7 =x + 32/21 ` ` (2)`
Thay `(1) (2)` vào $(*)$
` => 3x - 2.( x + 37/15 ) - 4.(x +32/21) =54`
` ⇔ 3x - 2x - 74/15 - 4x - 128/21 =54`
` ⇔ -3x - 386/35 = 54`
` ⇔ -3x = 54 + 386/35 `
` ⇔ -3x = 2276/35 ⇒ x = - 2276/105`
` ⇒ y = x + 37/15 = - 2017/105`
` z = x + 32/21 = - 2116/105 `
