I didn't see that in the document. What page is it on?
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.
The questions are on page 215 (3/26) and Tao's answers are on the next page.
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.