a)The star ships Enterprise and Potemkin leave the Earth and travel in opposite directions each at 0.60c relative to an observer on Earth.In the Enterprise's frame of reference how fast is the Potemkin moving away?
b) Through what voltage must you accelerate a proton so that it achieves a velocity of 0.9999c?
a) There is a velocity addition formula:
(v1 + v2)/[1+v1 v2/c^2]
that you can use. However, the point of learning relativity is understanding how to derive such formulas from first principles, not to learn a list of formulas.
So, I suggest you study the Lorentz transformations and then how to derive the velocity addition formula from that. That derivation takes only one line.
b) The energy is gamma m c^2, if you express it in electron volts you get the voltage.
Again, this formula and the formula for relativistic momentum are derived from first princples and you must study this derivation. Simply being able to use the correct formula is not enough.