Dyscalculia is LD that has to with sight. That means your son would have trouble with reading and every other subjects. I would ask your son (since he is adult) to get tested for a LD in mathmatics. He could have that spefic LD. Ask your soon if he community college has an equal acess offic and have him contact them they will be able to help him with any trouble he is having truble in school.