Answer:
The well-known actress accepted the award.
Step-by-step explanation:
"the well known actress accepted the award" has several mistakes on it.
The first word doesn't have its first letter is capitalized. It should be since it begins the sentence.
When using an adjective and an adverb, it is not unusual to add a hyphen since it is meant to avoid confusion in the reading. "well-known" is a single concept and the hyphen helps with that idea.
The sentence should end with a period.