The total weekly sales for a newly released portable media player (PMP) increased each week. At the same time, the total weekly sales for another newly released PMP decreased each week. Models that approximate the total weekly sales S (in thousands of units) for each PMP are [S= 10x + 70 S = -10x +210 PMP 1 PMP2 where x represents the number of weeks each PMP was in stores, with x = 0 corresponding to the PMP sales on the day each PMP was first released in stores. After how many weeks will the sales for the two PMPs be equal?

In the summer, a certain lake’s water temperature is known to increase linearly with time. On June 1, the water temperature is measured at 40°F, and on July 1, it is 55°F. Which of the following represents the water temperature of the lake on July 31? a. 70°Fb. 65°Fc. 60°Fd. 75°Fe. 68°Ff. 72°F

Suppose that the number of tee shirts sold (N) depends linearly on the price charged (x). Write an equation showing this dependence.