Hi, I was taught that both " was/were able to " and " could " can be used to express ability in the past. Roughly speaking, " could " is not used with reference to one (or more) specific achievement in the past, but it can be used when referring to a general ability in the past (this, I think, is the case with your example from the Longman dictionary). uk/Practical-English-Usage-Michael-Swan/dp/0194420981 ") says: M.
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