To answer set up a proportion. You are trying to find how many books are in the entire book given 80% of the pages which is 180. Thus you put 80 over 100 and 180 over X(total number of pages). Then you cross multiply to solve for x.
remember the formula is/of. you have to put 180 pages over x because u don't know the total. then make that equal 80 over 100 to represent 80%. solve for the proportion how the person before me answered
