To solve this problem, we need to determine the value of x, which represents the number of books about animals that Dave bought.
Let's break down the information given:
Number of books about animals: x
Number of books about outer space: 6
Number of books about trains: 3
Cost per book: $6
Total cost of the books: $102
We can set up the equation as follows:
Number of books about animals * Cost per book + Number of books about outer space * Cost per book + Number of books about trains * Cost per book = Total cost of the books
x * 6 + 6 * 6 + 3 * 6 = 102
Let's simplify and solve for x:
6x + 36 + 18 = 102
6x + 54 = 102
To isolate x, we subtract 54 from both sides of the equation:
6x + 54 - 54 = 102 - 54
6x = 48
To solve for x, we divide both sides of the equation by 6:
x = 48 / 6
x = 8
The value of x is 8.
#### 8
The answer is: 8
Below is a math problem. Provide a detailed, step-by-step solution.

### Problem:
Dave bought x books about animals, 6 books about outer space, and 3 books about trains to keep him busy over the holidays. Each book cost $6. Dave spent 102 on the books.

### Answer:
