Out of the 31 chapters, Anna skips 31/3 = 10 chapters that are divisible by 3.
So, she reads 31 - 10 = 21 chapters.
If it takes her 20 minutes to read each chapter, then she spends 20 * 21 = 420 minutes reading.
To convert the time to hours, we divide by 60 since there are 60 minutes in an hour.
So, Anna spends 420 / 60 = 7 hours reading.
#### 7
The answer is: 7
Below is a math problem. Provide a detailed, step-by-step solution.

### Problem:
If Anna is reading a textbook with 31 chapters but skips all the chapters that are divisible by 3, and it takes her 20 minutes to read each chapter, what is the total amount of time she spends reading in hours?

### Answer:
