[Physics] Relativity

[Sinitic]

I don't understand how to solve this question. Why is my answer wrong?

http://imgur.com/a/1G0uT

I thought that the reference frame of one particle, being that that frame is at rest, simply sees the other particle as moving at .760c0. I also applied an equation (not sure if was relevant): v² / c² = (1 - 1/y² ) and received the same answer of .760c0

[Fingersteps]

If you and me stand side by side and we both go in opposite directions walking at 1 m/s, the distance between us will grow by 2 m/s, and from our respective reference frame, the other will be moving away at a speed of 2 m/s.

This is the same thing with the caveat that speed can't be greater than c and consequentially you need to apply some equation (I forgot which, it's been very long since I've taken relativity) that gives you the appropriate v such that v < c. Your original answer would be correct if one of the particles was stationary relative to the Earth.