fern has read 5/7 pages OF his 98 page book. I was taught that OF can mean to multiply.
so multiply 5/7 by 98 and you get 70.
70 is not the answer though . That is only how much he has rrad . and the question asks how much he has LEFT.
So Now subtract 98-70 . which equals 28
fern has 28 more pages left.