You know that the 2's must appear in the last three digits. First figure out how many numbers between 000 and 999 have at least one 2 (hint: it's 1000 minus the quantity of numbers in that range that have no 2's). This is the same as the quantity of numbers that at least one 2 between 3000 and 3999, or 4000 and 4999, or 5000 and 5999, etc.