His dining room is 4 walls and he has already removed 1 wall of wallpaper so that leaves 4-1 = <<4-1=3>>3 walls in the dining room
He has 3 walls left in the dining room and 4 in his living room for a total of 3+4 = <<3+4=7>>7 walls
It takes 2 hours to remove wallpaper from just 1 wall and he has 7 more to go so it will take him 2*7 = <<2*7=14>>14 hours
#### 14