Answer
0.34 c
Work Step by Step
Let the positive direction be the direction of your ship. Let your spaceship’s reference frame be S and the planet’s reference frame be S’.
The velocity of the planet relative to your spaceship is v = -0.90c. The velocity of the probe relative to the planet is u’=+0.95c.
Use the relativistic velocity addition formula, equation 26–10, to find the velocity of the probe as measured by your ship.
$$u=\frac{v+u’}{1+\frac{vu’}{c^2}}$$
$$u=\frac{-0.90c+0.95c}{1+(-0.90)(0.95)}=0.34c$$
