2). No 2 of the members sold the same number of tickets yesterday.

statement 2 means that no member sold the same # of tickets.

so the 3 members could have sold 100, 8, 53 tickets each, all of which are greater 2. But we want to know if at least one of them sold 2 tickets so we use the minimum number of tickets that could have been sold if every member sold a different # of tickets.

this is why we use 0 tickets sold for member#1, since 0 the least amount that could have been sold

next smalles number is 1. next is 2.

so for sure, the 3rd person would've sold 2 tickets.

Hope my explanation helps

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Impossible is nothing