The problem you provided can be solved using the concept of relative motion.
Her velocity has the components of 1.4m/s N and 2.2 m/s E so the net velocity has magnitude;
v = Sqrt(2.2^2 + 1.4^2) = Sqrt(6.8)
Therefore, the speed of Mary with respect to the shore is Sqrt(6.8) meters per second.
I hope it has come to your help.
