Complex sentence: In the U.S. many professional dancers belong to unions (such as the American Guild of Musical Artists, Screen Actors Guild and Actors' Equity Association) that establish working conditions and minimum salaries for their members.
Split into simpler sentences: In the U.S. many professional dancers are members of unions such as the American Guild of Musical Artists, the Screen Actors Guild and Actors' Equity Association. The unions help determine working conditions and minimum salaries for their members.