"问题公式化" can be translated into English as "formulate the problem" or "problem formulation" (as a noun phrase).
Formulate the problem (verb phrase): This emphasizes the action of transforming a vague or complex issue into a clear, structured, and often mathematical or logical expression for easier analysis or solution.
Problem formulation (noun phrase): This refers to the process or result of expressing a problem in a formalized manner, suitable for further study or resolution.