Once again, here is the issue: Q and Markan priority are by no means universally accepted (see e.g. Flusser, D. Jesus. Jerusalem: Magnes, 1969, revised 1998; Hengel, M. The Four Gospels and the One Gospel of Jesus Christ. London: SCM, 2000; Farmer, William. The Synoptic Problem. New York: Macmillan, 1964; Mann, C. S. Mark. Anchor Bible 27; Garden City, NY: Doubleday, 1986; Goulder, M. D. Midrash and Lection in Matthew. London: SPCK, 1974.)
In other words, there have been and continue to be arguments for and against.
The problem for you is that
1) Evaluating these arguments requires knowledge of Greek
2) You haven't even read them.
So why do you acccept Q and markan priority? Because you just hopped on that consensus bandwagon.