3⁹.(123 - x) = 2.3¹²
123 - x = 2.3¹² : 3⁹
123 - x = 2 . 3³
123 - x = 2 . 27
123 - x = 54
x = 123 - 54
x = 69
`3^9 . (123 - x) = 2 . 3^12`
`=> 123-x = 2 . 3^12 : 3^9`
`=> 123 - x = 2. 3^3`
`=> 123 - x = 2 xx 27`
`=> 123 - x = 54`
`=> x = 123 - 54`
`=> x = 69`