Solve the all parts of given problem:
Problem: A boat is traveling upstream in the positive direction of the x axis at 13 km/h with respect to the water of a river. The water is flowing at 8 km/h with respect to the ground.
Part A: What is the velocity of the boat with respect to the ground?
_____________km/h
Part B: A child on the boat walks from front to rear at 8 km/h with respect to the boat. What is the child's velocity with respect to the ground?
_____________ km/h
Any expert will able to provide correct answer for the above problem.