To make a shelf to display her teapot collection, Amina bought wood and nails. Each yard of wood costs $27 and each box of nails cost $4. She bought 6 fewer boxes of nails than yards of wood. Use this information for number 21 and 22.

21. Let x represent the number of yards of wood that Amina bought. Which expression could Amina use to represent the number of boxes of nails that she bought?

A. x

B. 4

C. x - 6

D. x + 6

22. Amina's total cost was $193. How many boxes of nails did she buy?

Since the number of nail boxes is 6 less than the number of yards of wood, the right expression to use is x-6. (x being the number of yards of wood) Now let us calculate the number of nail boxes she bought. Cost of x yards of wood at $27 per yard = 27x. Cost of x-6 boxes of nails at $4 per box = 4 (x-6) = 4x - 24 Therefore 27x + 4x - 24 = 193 31x - 24 = 193 31x = 193 + 24 31x = 217 x = 217/31 = 7 So she bought 7 yards of wood and 7-6 boxes of nail. That is, she bought only one box of nail.