First, we need to find the area of wall we need to cover. The room is 10 by 12 by 8 feet. I'm assuming that we only need to wallpaper the ceiling and side walls. It would be weird to wallpaper the floor when there is carpet/tiling.
Ceiling area:
![10 * 12 = 120](https://img.qammunity.org/2020/formulas/mathematics/middle-school/mh87labgmbttpp15pq3by29j0ptfa1idix.png)
Wall area:
![2(12 * 8)+2(10 * 8)=352](https://img.qammunity.org/2020/formulas/mathematics/middle-school/2c37fkttd4j7vxufdiwvip19i9u5zolmo6.png)
Total area:
![120+352=472](https://img.qammunity.org/2020/formulas/mathematics/middle-school/ollgfaw847o74a9bbb9er7mw47mfknsgvl.png)
Now, we subtract 15 feet for each window and door. There are two windows and two doors.
![472-4(15)=412](https://img.qammunity.org/2020/formulas/mathematics/middle-school/9te8bkzscfjmj7yysfo1xbpm4ye11w7v9y.png)
412 square feet of wall needs to be wallpapered. Dividing this by 70 (the square footage covered by one roll) gives something a little less than 6.
6 full rolls of wallpaper will be needed to fully wallpaper the room.