4.5 I'm pretty sure I hope I was right and hope this helps
Step-by-step explanation:
1. Octagon- 8 sides
2. Quadrilateral- 4 sides
3. Decagon- 10 sides
4. Nonagon- 9 sides
5. Octagon- 8 sides
6. Nonagon- 9 sides
<u><em>Hope this helps</em></u>
Cause that is not the answer it is 67

Since logs can't equal zero, 5 is your only solution.