By THE PULSE NEWS MEXICO STAFF    A new exhibit titled “Tres por Tres, Afromexicanos en Guerrero, Veracruz y Coahuila” (¨Three-by-Three: Afro-Mexicans in Guerrero, Veracruz and Coahuila”) is slated to open on Thursday, Aug. 8, at the Tlaxcala Regional Museum. The exhibit, composed of 18 photographs by three different photographers, shows how this marginalized community in Mexico has fought for its