
Please take a look a this online Gospel synopsis
here. This site allows you to easily scroll through Matthew, Mark, or Luke and find the parallel passages in the other gospels. If you clicking on the purple (Matthew), blue (Mark), or green (Luke) book icon beside the section heading, the appropriate column will automatically scroll to the parallel passage.
Read a portion of the Gospel of Mark and a parallel passage in the Gospel of Matthew, e.g., the "plucking the grain" story in Matthew 12:1-8 and Mark 2:23-28 or the "house divided" story in Matthew 12:25-27 and Mark 3:23-30.
As your "comment," note which version of the passage (if either) seems to you to be most likely the original version? In this passage does it look like Matthew is dependent on Mark, the Mark is dependent on Matthew, or that the the two gospels are giving independent accounts? Explain your thinking.