unfortunately this is impossible to tell out of context.
The passé simple is only used in literary French and practically never in spoken French. It is used when you are talking about an action which happened in the past, whose consequences are also contained in the past and don't extend to the present. Also, it indicates usually that the action happened at a certain time An example would be a story or fairy tale, "Once upon a time there lived a kind...."
The passé composé has all but replaced the passé simple. However, in deciding between the two you would tend to use passé composé for actions in the past which happen at an indefinite or unspecified time and whose results extend into the present.
J'ai trop mangé ce midi. -- I ate too much at noon.
Il a emprunté une importante somme d'argent. -- He borrowed an important sum of money.
La bataille de Marignan eut lieu en 1515. -- The battle of Marignon took place in 1515.
Jean se leva, sortit de la pièce et ne revint plus. -- Jean got up, left the room and didn't return anymore.