Which expression is equivalent to 2(a+2b)-a-2b?

Tom says that he needs 6 rolls to obtain each possible outcome on a 6-sided die. on the fourth roll, he rolls his second "3”. tom says that the die is loaded and that each outcome is not equally likely. is tom correct here? if you think tom is incorrect, how many rolls should tom make until he sees each number occurring about 1/6 of the time?