Answer:
2a-b
Step-by-step explanation:
We can start by grouping our A's and B's, while making sure to keep their individual signs.
For our A's, we get 3a-a and for our B's, we get 2b-3b.
When we simplify our A's, we get 2a and when we simplify our B's, we get -b.
After grouping them back together, you end up with 2a-b.
