Furthering the equation i get

where as shown i obtained 12, 21 and -22 by calculating the normal. I then substitute a vector in the plane, i.e 4,1,6), giving you an equation

The equation can now be rewritten to the form

then

I'm not sure how to reorganize that equation to evaluate the d mentioned above. Any help /push in the right direction would be great!

Once this is done then I should be able to check my equation by seeing whether each of the given three points in the plane satisfies it right ?

Thanks a bunch