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

Answer: Option C

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