Mark 12:28-34
A Pharisee scribe receives a favorable response from Jesus, that he is "not far from the kingdom of God." What the scribe lacks instructs all disciples in the all-important truth of the lordship of Jesus.

Mark 12:18-27
Some Sadducees present Jesus with a "gotcha" question about belief in the resurrection of the dead. If God's word to Moses is true, and if the resurrection is true, then there is a problem. The Sadducees present a scenario in which these two things seem to contradict each other.
That is the way of skepticism. Skeptics and those determined to doubt everything can never be convinced beyond any doubt that they should become faithful.
Jesus shows that these kinds of apparent contradictions disappear when looking at the question in faith and hope. That is, knowing the power of God and believing his word, we can rest assured that God's promises answer all question.

Mark 12:13-18
Jesus teaches those who would be disciples in the Kingdom of God to pay their taxes and to let God use life experiences to stamp his own image on our heart.

Mark 12:1-12
In response to religious leaders who challenged his authority, Jesus tells a story identifying them as rebellious vineyard workers. The vineyard is fruitful, but these managers refuse to offer the "owner" his rightful share. In other words, God's people want to worship him, but the established religious leaders garner the glory for themselves.
This also motivated their rejection of Jesus and his obvious divine authority. So, Jesus lets them know that he is the promised deliverer of God's people. He is the appointed leader of the Kingdom of God. Though the ones with positions of authority reject Jesus, he is God's choice, and God will soon make it clear that Jesus is the "cornerstone" for the entire Kingdom of God project that is underway.
When the cornerstone of a building is laid, the dimensions for the whole thing are determined. It is only a matter of the process of building. When the building is ready to be finished, the last thing is to set the capstone, locking everything else in place. As disciples in the Kingdom of God, we rejoice that the cornerstone is laid and the capstone is coming soon.