4

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

• a quick set of four practice problems, on a topic of your choice (with solutions)?
• help solving a specific problem labeled #4 from a set?
• a brief explanation of a concept with four examples?
• a 4-step study plan for a topic?

If you tell me the subject (e.g., calculus, linear algebra, statistics, discrete math) and the level (undergrad intro, intro to proofs, etc.), I’ll tailor it. Or, paste the problem you want solved.