Solution
= Solution
The collinear <relativistic velocity addition> formula is
$$
u=\frac{v+u'}{1+vu'/c^2}.
$$
With both <velocities> directed toward Earth,
$$
\boxed{u=\frac{0.6c+0.8c}{1+0.48}=\frac{35}{37}c=0.946c.}
$$
The denominator keeps the result below $c$. Adding the two speeds by the Galilean rule would give an inadmissible $1.4c$.