Question

Mary needs to row her boat across a 200m wide river that is flowing to the east at a speed of 1.4m/s . Mary can row with a speed of 2.2m/s What is her speed with respect to the shore?

Answer 1

Assuming she is heading directly for the opposite shore, just add the vector velocities
v^2 = (1.4)^2 + (2.2)^2
as though the legs of a right triangle with
v the hypotenuse. Take the square root of v^2.

"Speed with respect to the shore" slightly ambiguous, but assume it includes along-the-shore and away-from-the-shore.