COULD OR WAS ABLE TO

Could is used to talk about a general ability in the past. Was able to is used to talk about an ability on a specific occasion in the past.

Could se usa para hablar de una habilidad general en el pasado. Was able to se usa para hablar de una habilidad en una ocasión específica del pasado.

• could
  When John was 16, he could already drive.
  At the age of seven, Lisa could already speak three languages.
  Matt was very smart, he could beat anybody in his class.
  
• was able to
  John got lost but he was able to get back home by taxi.
  When Lisa was in France, she was able to talk with the locals in French.
  In the final test, Matt was able to get the best score
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