1. The problem statement, all variables and given/known data Find the unit normal to the plane a + 2s - 2t = 15. What is the distance of the plane from the origin? 2. Relevant equations The normal to a plane is given by s x t For any plane, r.n = p [n = unit vector and p = constant] 3. The attempt at a solution Not entirely sure what I'm meant to be doing here as I'm not given any real values for the vectors s and t, so I can't see how to crossing them achieves anything. I'd be capable of crossing the two vectors if they were in component form, but not here. Obviously I'm missing something here, any help would be great. Many thanks, /Supra.