8 + 9f - 2 + 6f - 8f - 4 + 12.

Simplifying the expression:

8 + 9f - 2 + 6f - 8f - 4 + 12
Combine like terms:
= (8 - 2 - 4 + 12) + (9f + 6f - 8f)
= 14 + 7f

So, the simplified expression is 14 + 7f.