Let the boat speed in still water be b.
Let the current speed be c.
The speed going upstream is 20/4 = 5 mph.
The speed going downstream is 32/4 = 8 mph.
b - c = 5 ........(1)
b + c = 8 .......(2)
Adding equations (1) and (2) we get:
2b = 13
b = 13/2 = 6.5
Plugging in the value for b into equation (1) we find c = 1.5.
The boat speed in still water is 6.5 mph and the current speed is 1.5 mph.
Constant rate means it is linear so we don't have to worry about fluctuation.
change in y/ change in x=-18-(-25.2)/5-8=2.4 meters per second
12(20-17) - 3*6
12 (3) - 18
12*3 - 18
36 - 18
18
