Question

The states New Jersey, Alaska, and Michigan have different ages for people to legally drive.

which amendment is this?

Answer 1

The 10th amendment, which is powers reserved for state governments

Answer 2

The Tenth Amendment says the powers not delegated to the United States by the Constitution, not prohibited by it to the States, are reserved to the States respectively, or to the people. So basically it gives the states freedom to decide what they want with the smaller decisions.