I wanna sell these games at gamestop?

i wanna sell silenthill coming, army of two 40thday,little big planet game of the year edition, medal of honor airborn,condemned two:bloodshot. dangerous hunt2009. i ave the power up card and it says 5 games is 20%more plus 50% do u think ill make about 30$ dollars of this cuz i dont even played them so idc ? and do i need a grown up to sell them and there all ps3 games