What is supporting evidence that he became a successful author from question number 3?

In 1930 his first novel, Not Without Laughter (Knopf, 1930), won the Harmon gold medal for literature.

Hughes's first book of poetry, The Weary Blues, (Knopf, 1926) was published by Alfred A. Knopf in 1926

Criticism of the book from the time varied

He finished his college education at Lincoln University in Pennsylvania three years later

The supporting evidence that he became a successful author includes winning the Harmon gold medal for literature with his first novel, Not Without Laughter, being published by a reputable publisher, Alfred A. Knopf, and finishing his college education at Lincoln University. Additionally, the criticism and recognition of his work further showcase his success as an author.