How do I know that the correct translation should include "how" ie. why is it not "He knew to speak to everybody" (his mother had made it quite clear he had to before the party!). Would this be an acceptable alternative translation or is there something about "parler" that means you imply the word "how"? Thank you to anyone who can help.
This might be useful - it was for me https://www.thoughtco.com/french-word-tout-and-its-variations-1368964