Answer
$x+y+z=1$
Work Step by Step
The normal to the plane is $n=\lt 1,1,1 \gt$
We know that the standard equation of plane passing through the point $P(x_0,y_0,z_0)$ is written as: $a(x-x_0)+b(y-y_0)+c(z-z_0)=0$
Then, we have for the point $P(1,0,0)$
$1(x -1)+1(y -0)+1(z-0)=0$
or, $x-1+y+z=0$
or, $x+y+z=1$
