Question

sue has 7/8 of her book left to read. If she reads another 2/7 of the book, how much of the book will she have left?

Answer 1

Let B = how much of the book she has left to read.

B = 7/8 - 2/7

B = (49 - 16)/56

B = 33/56

Sue has another 33/56 left of the book to read.

Answer 2

First you have to make the fractions equal.
That gives you 49/56 and 16/56. 
Then you add them together and get 65/56.
So I guess she finishes the book. (not completly sure, werid)
Hope this helps