1. The problem statement, all variables and given/known data A signal (traveling at the speed of light) is sent from -4 ls (light seconds) towards a moving spaceship traveling at 0.866c. How long does it take for the signal to reach the ship? 2. Relevant equations I'm pretty sure its t=(delta)D/c-v But I continue to get the wrong answer with it. 3. The attempt at a solution using the equation above [rearranged from d(light) = (delta)d + vt]. I get 29 seconds. I do it by multiplying 4 ls by 3e8 and use that as my distance. according to a spacetime diagram I have, the answer should be around 12s (my diagram might be wrong, but it doesn't seem so). But I can't seem to get it with this equation.