I had a go, and obviously, x+4y has to be equal to or less that 64 because that is teh workforce.

64 has factors, 2, 4,8,16,32. so if x=2, 4y must be 62, but we can't get 62 so x can never be 2. is x=4, 4y must be 60 so y =15

-am i on the right lines? I can't see how I would manipulate the algebra to answer this one.