Combining Like terms

What are like terms?

Are the following examples of like terms?

4x + 3

give an example of three like terms:

give an example of three not-like terms:

combine like terms for the following:

2x + 3x

combine like terms for the following:

13x - 4x

combine like terms for the following:

2x - 4 + 4x

combine like terms for the following:

3x + 3x - 4x

combine like terms for the following:

10x + x - 4

combine like terms for the following:

10 - x + 4x