Speed of Ferry is towards North with magnitude 6.2 m/s
Here if we assume that North direction is along Y axis and East is along X axis then we can say
[tex]\vec v_f = 6.2 \hat j[/tex]
Now a person walk on ferry with speed 1.5 m/s towards east with respect to Ferry
so it is given as
[tex]\vec v_{pf} = 1.5 \hat i[/tex]
also by the concept of relative motion we know that
[tex]\vec v_{pf} = \vec v_p - \vec v_f[/tex]
now plug in all values in it
[tex]1.5 \hat i = \vec v_p - 6.2 \hat j[/tex]
[tex]\vec v_p = 1.5 \hat i + 6.2 \hat j[/tex]
now if we need to find the speed of the person then we need to find its magnitude
so it is given as
[tex]v = \sqrt{1.5^2 + 6.2^2}[/tex]
[tex]v = 6.37 m/s[/tex]