Answer
0.78 c
Work Step by Step
Let the positive direction be the direction of both rockets. Let rocket A’s reference frame be S and the Earth’s reference frame be S’.
The velocity of the Earth relative to rocket A is v = -0.65c. The velocity of rocket B relative to the Earth is u’=+0.95c.
Use the relativistic velocity addition formula, equation 26–10, to find the velocity of rocket B as measured by rocket A.
$$u=\frac{v+u’}{1+\frac{vu’}{c^2}}$$
$$u=\frac{-0.65c+0.95c}{1+(-0.65)(0.95)}=0.78c$$