An observer on Earth sees an alien vessel approach at a
x w, vht6cc-jd3k 6fc, 3wkv lk+;1ambspeed of 0.60c. The Enterprise comes to
mjtd 3k ,ck;f63 cxv6aw1k -bv,c+whlthe rescue (Fig. Below), overtaking the aliens while moving directly toward Earth at a speed of 0.90c relative to Earth. What is the relative speed of one vessel as seen by the other? u =
c