Abook club charges a membership
fee of $20 and then $12 for each
book purchased.
write an equation when y, the total
cost is a function of x, the number of
books purchased

Atourist boat is used for sightseeing in a nearby river. the boat travels 2.4 miles downstream and in the same amount of time, it travels 1.8 miles upstream. if the boat travels at an average speed of 21 miles per hour in the still water, find the current of the river.