How Do Relative Velocities Transform in Special Relativity?

[wansui]

If A is moving to the left at a speed of 0.9c relative to E, B is moving to the right at a speed of 0.7c relative to E.

In the reference frame of A, what is the speed of B?
In the reference frame of A, what is the speed of E?
In the reference frame of B, what is the speed of A?
In the reference frame of B, what is the speed of E?

 

[JesseM]

Have a look at this page:

http://www.math.ucr.edu/home/baez/physics/Relativity/SR/velocity.html

Try to see if you can answer your own questions using the equations there, and then post again if you're still having trouble. Also, note that speed in special relativity is symmetrical between any two reference frames--if in my frame you are moving at speed v relative to me, then in your frame I will also be moving at speed v relative to you.