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Joanne was making repairs to her deck and needed to buy some supplies. She purchased two posts, three boards, and four piers for . When she needed more materials, she went back to the lumberyard and bought one post and five boards for . Realizing she did not need the piers, she made a third trip in which she bought three more boards, returned the four piers, and ended up with a refund of . What was the cost of each item?

Define variables for the number of posts, boards, and piers.

Write three equations with the three unknowns.

First Equation:
If # of posts; # of boards; # of piers, then .