Final answer:
To determine the speed of the boat relative to the shore, we need to add the speed of the boat relative to the water and the speed of the water relative to the shore.
Step-by-step explanation:
The speed of the water in the river and the speed of the motorboat relative to the water are provided in the question. To determine the speed of the boat relative to the shore, we need to consider the velocities of the boat and the river.
The speed of the boat relative to the shore can be found by adding the speed of the boat relative to the water and the speed of the water relative to the shore.
For example, if the water in the river is moving south at 3.0 m/s and the motorboat is traveling due east at a speed of 8.0 m/s relative to the water, then the boat's speed relative to the shore would be (8.0 m/s) + (3.0 m/s) = 11.0 m/s.