The formula t= + gives the
total time t (in hours) needed for a
boat to travel upstream a distance
of d miles and then back
downstream the same distance,
where b is the speed of the boat in
still water and c is the speed of the
river's current (both in miles per
hour). How can you write a formula
that gives the speed of the current
in terms of the other variable? What
is the formula? (3 points)

Barney & noblet customers can choose to purchase a membership for $25 per year members receive 10% off all store purchases 1. how much would a member pay per year if he bought $50 worth of items each year? 2. write a slope-intercept equation that expresses how much a member pays per year using x to represent his purchases per year 3. how much would a member have to spend per year to pay off his membership fee?