I think they mean at the bottom of p216 (pdf page 4), where he says he doesn't know, r+s=80 but there isn't enough information to solve for r and s.
replyThere's two questions that are intended to be wrong (probably to test confidence). One with insufficient information and where the question itself implies falsehoods.
replyThe questions are on page 215 (3/26) and Tao's answers are on the next page.
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