Answer:
20 km/h
Step-by-step explanation:
Let b represent the speed of the boat in km/h. Then the distance covered is ...
distance = speed × time
(b -2)(11) = (b +2)(9)
11b -22 = 9b +18 . . eliminate parentheses
2b = 40 . . . . . . . . add 22-9b
b = 20 . . . . . . . . . divide by 2
The speed of the boat is 20 km/h.
