The graph below shows the amount of money left in the school’s desk fund, f, after d desks have been purchased.
a graph titled desk fund amount. the horizontal axis shows the number of desks purchased (d), numbered 1 to 9, and the vertical axis shows the dollars left in fund (f) numbered 100 to 800. blue diamonds appear at points (0, 700), (1, 590), (2, 480), (3, 370), (4, 260), (5, 150), (6, 40).
for each new desk that is purchased, by how much does the amount of money left in the school’s desk fund decrease?

Isuck at math ; ^; m a student solved this problem and said the answer is 3 feet. chase had a roll of ribbon that contained 7 7/8  feet of ribbon. he cut off one piece that was 3 5/8  feet long and another piece that was 1 1/4  feet from the roll. how much ribbon was left on the roll? is the student's answer reasonable? yes, the answer is reasonable. no, the answer is not reasonable. it should be about 2 feet. no, the answer is not reasonable. it should be about 13 feet. no, the answer is not reasonable. it should be about 4 feet.