Final answer:
The sentence contains seven nouns, which include names of people, a place, and ideas.
Step-by-step explanation:
The sentence 'Carl, Shane, and Seth went to the retreat for citizens who want peace and equality in our society.' contains seven nouns. These nouns are: Carl, Shane, Seth, retreat, citizens, peace, and equality. It's important to note that nouns are words that name people, places, things, or ideas. In this sentence, 'Carl', 'Shane', and 'Seth' name people; 'retreat' names a place; 'citizens' denote a group of people; and 'peace' and 'equality' represent ideas.