20:4

It seems you might be referring to a numerical ratio or perhaps a time format, but without more context, it's not clear what kind of assistance you are looking for. If you're studying for university exams and dealing with ratios or time-related questions, please provide more details so I can assist you further. If "20:4" refers to something specific in your study materials or is related to a particular subject area or concept you're trying to understand, please give me more information.