After 80 minutes Dorothy had read 120 pages of a 300-page book if she cotinues reading at the same rate about how long will it take her to rea the entire book?

It will take her 160 minutes to read 240 pages so...

*Starts scribbling furiously at some paper, attempting to find the answer*

... if I am a mathematical genius of a 12 year old (which I am) the answer is...

*pauses to build suspense*

... 200 minutes! (I think)

Hope my antics have helped!