"Storekeepers know how to sell and buy."
Translation:Les commerçants savent vendre et acheter.
generally savoir + infinitive means to know how to do something
However there is an exception to this rule, namely:
Anything that involves a process (like building a radio, baking a cake, etc.) requires savoir + comment.
Il sait comment faire une radio. - He knows how to make a radio.
Je sais comment m'y rendre - I know how to get there
il sait comment faire un gateau - he knows how to make a cake
I thought the same, but found this link explaining the differences between using les or des. https://forum.duolingo.com/comment/3683850/Les-or-Des
Why is it "les" instead of "des"?
The sentence does not say "The" storekeepers; it says only "Storekeepers."
I thought that when "the" is missing, the required replacement is "des," meaning "some." For example, in this same series of exercises, when asked to write "Students drink wine," I've repeatedly said "Des etudiants boivent du vin," and it was deemed correct.
The English sentence is expressing a generality. In French generalities use definite articles.
Generalities associated with uncountable nouns will use either le or la and generalities for countable nouns will use les.
Note that all appreciative verbs (aimer, adorer, détester, préférer) introduce generalities.
Les poules sont des oiseaux - Hens are birds.
Même les enfants auraient été meilleurs que moi - Even children would have been better than me!
il préfère la bière. - he prefers beer.
Thanks for that clear, helpful response. So I guess the fact that duolingo accepts "Des etudiants boivent du vin" is because, of course, all students do not necessarily drink wine; some do, some don't. Whereas, all hens are chickens; therefore, "Les poules sont des oiseaux." Aha! Merci!