I believe that each of the four sentences is punctuated correctly.<br/>Do you agree?<br/><br/>1) The eighties' greatest actor was Sylvester Stallone.<br/><br/>2) The '80s' greatest actor was Sylvester Stallone.<br/><br/>3) The greatest eighties actor was Sylvester Stallone.<br/><br/>4) The greatest '80s actor was Sylvester Stallone.<br/><br/>Thank you.