1. 2a + b = ?

2. x + y + x + y = ?

3. x + y + x = ?

4. c + 2d + c - 2d

5. ( a + 5 b ) - 5b

6. 5x - y - ( 4x - z ) = ?

7. q - p + p - q = ?

8. subtract x - 4 from 4x - y

9. x - y = ?

10. When a number and a variable are stuck together with no symbols, you should ____________.