sally read 21 pages of a book on Satuday. She read 5/9 of the remainder on Sunday. If she still had 1/3 of the book left to read, how many pages were there in the book?

Answer 1

number of pages ---- x

at end of Saturday, number of pages left = x-21
she read 5/9 of those, leaving 4/9(x-21) pages

but this is supposed to be 1/3 of the pages

4/9(x-21) = (1/3)x
times 9
4(x-21) = 3x
4x - 84 = 3x
x = 84

There were 84 pages in the book

check:
she read 21 pages on Saturday leaving 63
on Sunday she read 5/9 of that or 35 pages
leaving her with 28 pages to read
and 1/3 of 84 = 28