Answer:
2x and 5x are like terms, 2x and 3y are not. 3 and 5 are like terms, 6y and 2 are not. etc.
Explanation:
For something to be a like term, they either have to have the same variable (ex: x and y and any other variable that may be used) or both be whole numbers (1, 2, 3, etc.) No mixing the two.