A carpenter purchased 60 ft of redwood and 90 ft of pine for a total cost of $336. A second purchase, at the same prices, included 80 ft of redwood and 60 ft of pine for a total cost of $364. Find the cost per foot of redwood and of pine.

Afarmer has a large field that is x feet in length. he wants to fence in a rectangular section in the middle of the field , leaving a length of 100 feet of open field behind each end of the fenced rectangle. he also wants the width of the fenced-in space to be 100 feet less than its length. find the expressions to represent the length and width of the fenced section of the field