Say hi Bob! ("Hi Bob") Bob's 30 and still lives with his mom
And he don't got a job, cause Bob sits at home and smokes pot

from Eminem – The Kids Lyrics on Rap Genius

Meaning

Pot (Marijuana) has an effect on people lowering their motivation, making them lazy. Bob is too lazy to get a job to make money and move out and get his own house.

I think it’s also a pun on how dumb Bob is: Shady asks Bob to say hi (to the class) (say hi, Bob) but he misinterprets this simple order and says ‘hi Bob!’ instead…

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