Well this question is commonly referred to as the ‘synoptic problem’ which as O’Donnell points out is an ‘investigation into the existence and nature of the literary interrelationship among the first three "synoptic" gospels.’ The Gospels of Matthew, Mark, and Luke are called the ‘synoptic’ gospels, in contrast with the Gospel of John, because they can be readily arranged in a three-column harmony structure called a "synopsis." Unlike the Gospel of John, the Synoptic Gospels share a great number of parallel accounts and parables, arranged mostly in the same order and told with many of the same words. Any proposed logical solution to the synoptic problem therefore must account for these literary similarities among the Synoptic Gospels, not so much in terms of their factual content, but in the selection of that content, the arrangement of the material, and wording of the parallels. However, the ‘Synoptic Problem’ for many scholars is not really a "problem" in the normal sense of the term. It can simply be seen as a way to refer to questions and try and formulate possible explanations about the literary relationships between the first three of the New Testament Gospels. The word "synoptic" comes from the Greek word which means "with the same eye" or "seeing together." Matthew, Mark, and Luke seems to present the basic story of Jesus in similar ways, including the order of the material, the stories told, the sayings of Jesus, even using many of the same words in many of the parallel accounts. For this reason they are called the Synoptic Gospels. On the other hand, while the Gospel of John sometimes resembles the other three Gospels, it tells the story of Jesus in significantly different ways, including a different order of events, different perspectives and points of emphasis, and with its own unique vocabulary and style. Those differences can be understood in terms other than literary relationships between the Gospels, which is the reason John is not included in the Synoptic Problem. The synoptic problem can therefore be seen as the cornerstone of the historical and critical scholarship of the gospels. As a result, one's solution to the synoptic problem will influence a persons exegesis, redaction criticism, and form criticism of the gospels as well as the quest for the historical Jesus, the early church history, and even in some respects, the text of the gospels and it is to the text of the Synoptic Gospels where I will now begin my analysis.
W.R.Telford, in his short introduction to the New Testament, outlines that where content is concerned, the number of ‘pericopae shared in Matthew, Mark and Luke is extensive.’ Statistics show that only a small number of verses are
Donnell, K, 1999. Introduction to the New Testament. London; Hodder and Stoughton
Telford, W R, 2002. The New Testament: A Short Introduction. Oxford; Oneworld Publications