Ok, so 120 pages plus the 60% of the book she has left to read will give the total number of pages.
That means that 120 pages is 40% of the book.
Make a proportion
120/40% = x/60%
72 = .4 x
x = 180 pages
D because one thousand nine hundred twenty divided by 8 equals two hundred and forty
Ok so basically your going to subtract 57-8 which is 49. So now you have 7y=49 so now divide 49 by 7 which is 7. So your answer is 7 and to check your work substitute 7 for y so.... 7(7)+8=57 so 57=57 which is accurate