十中八九
ji-.chuu.ha-.kku
(or ju-.chuu.ha-.kku)

Literally: ten – middle – eight – nine

Alternately: Eight or nine out of ten; an 80% – 90% probability; “most likely, X”

Notes: This is obviously in the same vein as the previous 九分九厘, and may be considered equivalent, although in a purely mathematical sense the chances are lower and so the certainty is less absolute.

Also, this manjuu – image sourced here.