First calculate how much wallpaper is needed:
add: 2 walls of 12.5 ft length x 8 ft high = 200 ft²
add: 2 walls of 10.5 ft length x 8 ft high = 168 ft²
subtract: 2 windows of 4 ft length x 3 ft high = 24 ft²
subtract: 1 door of 3 ft length x 7 ft high = 21 ft²
Wallpaper needed: 200 + 168 - 24 - 21 = 323 ft²
Add 10% for waste and matching: 323 + 323(10%) = 355.3 ft²
Next, calculate the amount of wallpaper in one roll:
0.5 ft wide x 30 ft length = 15 ft²
Lastly, calculate how many rolls are needed:
355.3 ÷ 15 = 23.7
Since you can only purchase an entire roll (and not a fraction of it),
round the answer up to the nearest whole roll.
Anser: 24 rolls of wallpaper should be purchased.