Yes, this problem becomes obvious if you assume that it's ok for the tax collector to have 0 cookies and you work the problem from the last stop.

2 = x * .5 + 1 ==> 2

The aha moment is realizing that every tax collector if willing to give up his cookie and have none then would be for you to leave with 2 cookies.

The temptation is to not to think about the problem in practical terms but to use your powers of mathematics to overthink this problem. Both solutions show intelligence - which candidate do you want on your team? The one who solves problems practically and sometimes empirically or the one who resorts to deep analysis?

Of course the answer depends on the job you are hiring for. As always YMMV...