If p is the number of pages read on weekdays, then on Saturday and Sunday he reads x+30 pages on each of the two days. Therefore 5x+2(x+30)=473. That is, 7x+60=473, 7x=413, x=59 pages.
(Another approach is just to use arithmetic directly: if the book had 60 fewer pages, that is, 413 pages instead of 473, he would read the same number of pages for the whole week, so he would read 413/7=59 pages a day.)
Wednesday is a weekday, so he reads 59 pages.
