4

Not sure what you mean by "4". Do you want:

• a 4-question practice quiz in a subject, at a certain level?
• help solving a specific problem (problem #4) you’re stuck on?
• explanations or flashcards on a topic (the 4 most important points)?
• something else?

If you want a quick 4-question quiz, tell me the subject (e.g., math, physics, stats), level (high school, undergrad), and difficulty, and I’ll generate it with solutions. Or paste the problem you’re working on and I’ll walk you through it.