Simple Analytic Geometry Question

Find a vector perpendicular to the plane (1 1 1).

Super easy I know, but for some reason I can't find out how to get the vector...

This is Analytic Geometry, and therefore I am changing the title

Hint: Cross products.

n x plane = (0 0 0) ?

n x vector = (1 1 1) ?

From intuition the vector should be 111 or -1-1-1.

I've looked all over the internet and my old textbooks. This is a simple question and I've done this type of stuff over 4 years ago. I'm now in my 3rd year of engineering and finding this vector is a tiny part of answering a much, much bigger question (critical resolved shear stress in an FCC crystalline structure).

I worked out the final answer with 111, and it seems wrong. Answer was 0.933MPa when it should lie between 50-100psi.