Shae is covering 3 walls in her bedroom with wallpaper. the measurement of each wall is 12 ft x 14 ft. a roll of wallpaper covers 42 square feet. how many rolls should shae purchase?

Each wall measures 12 ft * 14 ft.
Area of one wall = LW = 12 ft * 14 ft = 168 ft^2
Area of 3 walls = 3 * area of 1 wall = 3 * 168 ft^2 = 504 ft^2

One roll of wall paper covers 42 ft^2.
To find out how many rolls are needed,
divide the total area by the area of one roll.

(504 ft^2)/(42 ft^2) = 12

Shae should purchase 12 rolls.