Ummm I need more infooooo...
If we let
be the number of pages read in 1 hour, then in 7 hours Doug reads
pages. We know that this number of pages is 231, so we have

You are missing part of the question
OK.......
Evaluating [(21 + 6) - 32] 2 * 9

Your answer would be
-90
H0P3 It H3LPS :)