`401 - 2005 : (2006- x)=0`
`2005 : (2006- x)= =401 - 0`
`2005 : (2006- x)=401`
`2006-x = 2005 : 401`
`2006-x = 5`
`x=2006-5`
`x=2001`
`=> 2005 : (2006 - x) = 401`.
`=> 2006 - x = 5`.
`=> x = 2001`
\(401 - 2005 : ( 2006 - x ) = 0\)
\( 2005 : ( 2006 - x ) =401 - 0\)
\( 2005 : ( 2006 - x ) =401\)
\( 2006 - x = 2005 :401\)
\( 2006 - x = 5\)
\( x = 2006 - 5=2001\)