"Jūchū-hakku十中八九" means "eight or nine out of ten" - very likely or almost certain. It expresses high probability, like saying "nine times out of ten" or "most likely" in English. EX. 「彼（かれ）は一生懸命（いっしょうけんめい）勉強（べんきょう）したから、十中八九（じゅっちゅうはっく）試験（しけん）に合格（ごうかく）するだろう！」 "He studied hard, so there's a good chance he'll pass the exam!"