Answer: $555.50
Step-by-step explanation
One wall is 13 ft wide and 9 ft tall. This wall area is 13*9 = 117 square feet.
An adjacent neighbor wall is 9 ft wide and 9 ft tall. Its area is 9*9 = 81 square feet.
The total area of both these walls is 117+81 = 198 square feet.
Use the hint your teacher gave you to convert from square feet to square yards.

The square feet units cancel out when doing this conversion, which is why we need the "sq ft" in the denominator.
198 square feet converts to 22 square yards.
We can now find how much it will cost us.
1 square yard = $25.25
22*1 square yard = 22*($25.25)
22 square yards = $555.50 is the total cost