Please see the attached file.

Two spaceships, each of proper length 100 m, pass near each other heading in opposite directions. If an astronaut at the front of one ship measures a time interval of 2.50 x 10-6 sec for the second ship to pass him, then

(a) what is the relative velocity of the spaceships
Given a length and a time, divide one by the other to get the relative velocity
=

(b) What time interval is measured on the first ship for the front of the second ship to pass from the front to the back of the first ship?

Length travelled of the second ship when seen from the first = L0
= 100
Time measured = 99.1071/4*107 = 2.47768 microseconds.