If (x - 5)² + (y - 2)² + (z - 9)² = 0, then the value of (x + y - z) is?

$$\eqalign{ & {\left( {x - 5} \right)^2} + {\left( {y - 2} \right)^2} + {\left( {z - 9} \right)^2} = 0 \cr & {\text{It is possible only when }} \cr & x - 5 = 0 \cr & x = 5 \cr & y - 2 = 0 \cr & y = 2 \cr & z - 9 = 0 \cr & z = 9 \cr & \therefore x + y - z \cr & = 5 + 2 - 9 \cr & = 7 - 9 \cr & = - 2 \cr} $$