At the end of the FMA: Brotherhood (Fullmetal Alchemist) series, Edward tried to use alchemy and failed because he wanted his brother back and the law of equivalent exchange clearly states that
Humankind cannot gain anything without first giving something in return. To obtain, something of equal value must be lost.
Therefore Alphonse's alchemy would be an equal value to Edward's alchemy. so my question is if Edward Elric traded his brother's (Alphonse Elric) body and soul with his alchemy, why can't Alphonse trade his alchemy for Edward's alchemy?
Previously, it was asked Why can't Edward get back his power to do alchemy? That question was (in my perspective) saying Ed should use a philosopher's stone to do alchemy, because a philosopher's stone ignores the law of equivalent exchange. My question focuses on the observation that a transmutation by Al to give up his alchemy for Ed's should be a good example of following the law of equivalent exchange.