He scored 24 points which means that after scoring the 4 three pointers, he would have to score another 4 three pointers (12 points)
The change of the cost changes when the pounds of ham changes. When the pounds of ham is 0, it costs 0 dollars. When the pounds of ham is 3, it costs 12 dollars. The cost changes consistently with the pounds of ham. They change together. Every time the pounds of ham goes up by 3, the cost goes up by 12.
It typically just needs two parts
1) all parties must be in agreement
2) something of value needs to be exchanged. ie. money, a service
