Answer
a) $120m$
b) $150m$
c) $v=0.60c$
Work Step by Step
(a) It is given that that the ships are identical with the same relative speed; therefore, according to your point of view, your friend's ship is $120m$ long.
(b) We know that in the rest frame of your friend, he measured his ship to be $150m$. As both the ships are identical, you measure your ship in your rest frame as $150m$.
(c) We know that
$v=c\sqrt{1-\frac{L^2}{L_{\circ}^2}}$
We plug in the known values to obtain:
$v=c\sqrt{1-(\frac{120m}{150m})^2}$
$v=0.60c$
