The statement that best describes a time when the Supreme Court decided that a Texan exercised the right to free speech is:
when a group of students wore black armbands to protest the Vietnam War.
This refers to the landmark Supreme Court case Tinker v. Des Moines Independent Community School District (1969), where the Court ruled that students do not lose their first amendment rights to freedom of speech when they enter a school. The case involved students wearing black armbands to protest the Vietnam War, and the Court upheld their right to do so.