"Twelve divided by four"
Translation:Un deg dau rhannu pedwar
Because "deg dau" isn't a word. Even though "deg" is the word for "ten" we always say "un deg" if we are talking about one of the teen numbers and eleven and twelve. (at least in the decimal system, in the twenty based system you could say "deuddeg rhannu pedwar", but we rarely use the twenty system for maths now).