You can put this solution on YOUR website!
I just tried every single number that could be the one left out
First I let
= the amount one person paid and
amount other person paid.
, so the sum of
what they bought must be divisible by
The only way I could arrive at this is if the coin costing 20
is left out. Then
, so if
1 person bought 33 worth of coins
The other bought 66 worth
So, he kept the coin costing 20