The answer is B.
To get this answer you look at what you know first: Karen reads 100 pages a day while David reads 80 pages a day. These numbers make the equation 180d=10,000
You need to know how to add Rick in, and the only thing you know is that he reads 35% less than Karen which means that he would read 65 pages a day (get that by taking 100×.35 which equals 35 then you take 100-35 and get 65 because he reads 35 pages less than karen). To finish, you need to add Rick into the equation with Karen and David, so you add 65 to 180 and get 245. This number replaces the 180 in the equation so that the final equation is 245d=10,000
