Edit. I think the topic is misinformative and I dont know how to change it. Hey I have to translate this into english so bear with me. Two spaceships are approaching earth from two directions along the x-axis. Earth observer(EO) calculates their speeds to be 0,8c each. Calculate at what speed EO observes them to be approaching each other. Is c the maximum speed in situations like this or can you just add the speed together -> 1,6c?