Original sentence: She participated in several exhibitions in the 50's: with the American Watercolor Society, the Metropolitan Museum's European traveling exhibition, the Washington County Museum of Art, a solo exhibition at Gettysburg College, at the York (PA) Art Center, and in New Canaan, CT
Edited sentence: She participated in several exhibitions in the 50's: with the American Watercolor Society, the Metropolitan Museum's European traveling exhibition in 1956-57, and in 1958 at the Washington County Museum of Art , a solo exhibition at Gettysburg College, at the York (PA) Art Center, and in New Canaan, CT