"In 1988 my Grannie was quite a bit older than Grandpa. In fact the difference between the squares of their ages (amazingly!) was exactly 1988.... How old were they?"

My workings:

x^2-y^2=1988

(x+y)(x-y)=1988

(x+y) or (x-y) must be even

x or y must be even

Now I'm stuck

any help?