Shae is covering 3 walls in her bedroom with wallpaper .the measurement of each wall is 12ft x14 ft a roll of wallpaper covers 42 square feet . how many rolls should shae purchase

1 wall is 12x14 so that's 168 square feet
it's 3 walls so 3x168 is 504
each thing of wallpaper covers 42 square feet so divide 504 by 42 (and if you have a fraction/remainder, round up)
504/42 is 12 though so you don't need to round, the answer is just 12