Would you be mad....?

yes and no it depends if they are just friends or if the girl like him and he know that and he tries to put the moves on her also if he didn't tell me

Hell yes. But I would talk about my feelings and we'd get over together.

Poloprince :]

so when you are not available he has a substitute? look if he is friends with this girl that's cool. but if it was someone he did not know well, that would be different. did he tell you that he would ask some else? the thing is it can be read both ways but if he has this behavior with you every time you are not available then yes i would be mad too.

Maybe he had already purchased the tix and needed someone else to go so he didn't waste six bucks?

Yeah, cause he might like the girl and if you don't go then you have no clue what could have happened while you werent there. Believe me, I have had that experience.

Yes, because I would be a little worried what would be going on but if you can trust him and the girl than ok but if you don't even know that girl I don't know.