ok, i'll try to put kgm's explanation in lamen's:

now tha first part of the math: the 5 dollars back--simple-- 30 - 5 = 25

right now there is 25 paid for the room...

then, the math for the five dollars --also simple-- (5 - 2) = 3 , 3 / 3 = 1

so each gets one dollar apiece...

now, forget 9 paid multiplied by 3 for each payin and instead look at the 3 dollars that comes back from the refund...

add this to the 25 dollars that is paid for the room...

--simple--

25 + 3 = 28

the rest should be easy for grade schoolers:

30 - 28 = 2

this is the 2 dollars that the bellboy gets...

25 + 3 + 2 = 30


and that's just logic...

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