SOLUTION: a boat can travel 18 miles against the current in 2 hours. on the return trip, the same distance is traveled in 1.2 hours. find the speed of the boat in still water and the speed o

Let x = the speed of the boat in still water,  and
let y = the speed of the current.


The "speed equation traveling upstream" is

 = x - y       (18 miles divided by 1.2 hour = the speed traveling upstream = x - y)



The "speed equation traveling downstream" is

 = x + y      (18 miles divided by 1 hour = the speed traveling downstream = x + y)



Rewrite it as the system

x - y =  9     (1)
x + y = 15     (2)


Add equations (1) and (2). You will get

2x = 15 + 9 = 24  ====>  x =  = 12.


Then from (2)  y = 15 - 12 = 3.


Answer.  x = 12 mph;  y = 3 mph.