Answer
$15.3\frac{m}{s}$
Work Step by Step
We can find the required speed as
$\vec{v_{at,g}}=\vec{v_{at,p}}+\vec {v_{p,g}}$ where 'at' , 'p' and 'g' represents attendant, airplane and ground respectively.
We plug in the known values to obtain:
$\vec v_{avg}=(-1.22\frac{m}{s})\hat x+(165\frac{m}{s})\hat x$
$\vec v_{avg}=15.3\frac{m}{s}$
