Answer: 3, 3, and 8.
Explanation: As Reddit users TT1103 and RedditRage explained, the key to this brain teaser is that the census taker looks at the house number. In other words, she knows the sum of the children's ages.
However, at that point of the riddle, she still can't tell how old the man's children are. Therefore, she has to be stuck between multiple possibilities. To narrow it down further, only two sets of numbers that multiply to 72 share the same sum: (2,6,6) and (3,3,8).
After the man reveals that his oldest child likes chocolate pudding, however, the census taker can differentiate between the two options. That is, only the latter of those two sets has a distinct "oldest" child.
Source: mikebrown_pelican, Reddit
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