Okay, this may be a stupid question, but I'm confused.

I've just gained my first calculator character, I've purchased a few abilites for the job class, this person also has Black Magic as secondary skill.

My problem is that I cannot use the Math Skill. It states that I do not have any combo abilities....I'm not sure what this means. I have the "5" ability and combined with the black magic spells, why am I not able to use Math?

Any insight would be helpful.