Answer:
Explanation:
In general you can always add terms that are similar to each other: similar means that they have the same variables.
For example you can say: 3 bananas + 2 bananas = 5 bananas (3x+2x=5x)
But you can't say; 3 bananas + 2 apples = 5 something (3x+2y=3x+2y : can't add them).
Example in a: 3x+4y+2x+y you have 2 terms with x and 2 terms with y, those are similar and you can add them:
3x+4y+2x+y=6x+5y
Other than this you can't proceed since 6x and 5y aren't similar