P versus NP is considered as one of the most important open problems in computer science. This consists in knowing the answer of the following question: Is P equal to NP? It is one of the seven Millennium Prize Problems selected by the Clay Mathematics Institute. This question was first mentioned in a letter written by John Nash to the National Security Agency in 1955. A precise statement of the P versus NP problem was introduced independently in 1971 by Stephen Cook and Leonid Levin. Since that date, all efforts to find a proof for this problem have failed. To attack the P versus NP question the concept of NP-completeness has been very useful. If any single NP-complete problem can be solved in polynomial time, then every NP problem has a polynomial time algorithm. MONOTONE 3SAT is a known NP-complete problem. We prove MONOTONE 3SAT is in P. In this way, we demonstrate the P versus NP problem.