Des becomes de when the adjective is before the noun.
Why isn't it "Des bonnes fraises"?
As a general rule, "des" becomes "de" in front of an adjective.
in a previous sentence the opposite was given i.e. de becomes des in front of an adjective (?)
Perhaps you misread the comment from the previous thread.
Yes, but how do we know from pronunciation whether the speaker is referring to "some good strawberries" or "good strawberry" ?
in singular, it would have been "UNE bonne fraise".
Wouldn't the female form be "de la"?
No, "de la" is used with uncountable substances, like "de la soupe" and "de la" is necessarily singular.
strawberries are countable, so singular "une fraise", plural "des fraises"
now, if you add an adjective just after "des", it becomes "de"
Thanks for the explanation regarding de and des - much appreciated!