Andrew's bedroom required 8 planks.
The guest bedroom required 2 fewer planks than his bedroom, so it required 8 - 2 = 6 planks.
The living room required 20 planks.
The kitchen required 11 planks.
Each hallway required 4 planks, and there were 2 hallways, so the total for the hallways is 4 x 2 = 8 planks.
So far, Andrew needed 8 + 6 + 20 + 11 + 8 = 53 planks.
He also had to replace 3 planks in each bedroom, so that's 3 x 2 = 6 planks.
He ended up with 6 leftover planks.
Therefore, Andrew initially bought 53 + 6 + 6 = 65 planks for his hardwood flooring installation.
#### 65
The answer is: 65
Below is a math problem. Provide a detailed, step-by-step solution.

### Problem:
If Andrew's bedroom required eight wooden planks, his living room required twenty planks, and his kitchen required eleven planks, how many planks did Andrew initially buy for his hardwood flooring installation, considering that the guest bedroom required two fewer planks than his bedroom and each of his two hallways required four planks? Additionally, he had to replace three planks in each bedroom due to furniture damage and ended up with six leftover planks.

### Answer:
