Test 3 Section 5 - #16 (page 530)

Well, according to the way the problem is set up, we're going to have one "1", two "2"'s, three "3"'s, etc.  We want to know when the first "12" will come.  Well, that's going to come after the eleventh "11".  Let's just count up how many terms will come first:

1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 + 11 = 66

So if 66 terms come before the first "12", the first "12" will be the 67th term.