Final answer:
The contractor should order 6.67 cubic yards of concrete.
Step-by-step explanation:
To find the volume of the wall, we can use the formula V = lwh, where l is the length, w is the width, and h is the height. In this case, the length is 24 feet, the height is 10 feet, and the thickness is 9 inches. However, we need to convert the thickness from inches to feet. Since there are 12 inches in a foot, the thickness is 9/12 = 0.75 feet. Substituting these values into the formula, we get V = 24 * 10 * 0.75 = 180 cubic feet. To convert cubic feet to cubic yards, we divide by 27 (since 1 cubic yard = 27 cubic feet). Therefore, the contractor should order 180/27 = 6.67 cubic yards of concrete.