Question

За 2 книги и 3 тетради заплатили 18 рублей.Книга дороже тетради в 3 раза.Сколько стоит книга?

Answer 1

1) 3*2х+3х=18
6х+3х=18
9х=18
х=18:9
х=2 руб. стоит одна тетрадь
2) 2*3=6 руб. стоит книга

Answer 2

Problem Analysis

We are given that the total cost of 2 books and 3 notebooks is 18 rubles. It is also mentioned that the book is 3 times more expensive than the notebook. We need to find the cost of the book.

Solution

Let's assume the cost of the notebook is x rubles. According to the given information, the cost of the book is 3 times the cost of the notebook, which means the cost of the book is 3x rubles.

The total cost of 2 books and 3 notebooks is 18 rubles. We can set up the following equation to represent this information:

2 * (cost of book) + 3 * (cost of notebook) = 18

Substituting the values we found earlier, we get:

2 * (3x) + 3 * x = 18

Simplifying the equation:

6x + 3x = 18

Combining like terms:

9x = 18

Dividing both sides by 9:

x = 2

Therefore, the cost of the notebook is 2 rubles. Since the cost of the book is 3 times the cost of the notebook, the cost of the book is:

3 * 2 = 6 rubles.

Answer: The book costs 6 rubles.

Verification

Let's verify our answer using the given information.

The cost of 2 books and 3 notebooks is 18 rubles. Substituting the values we found earlier:

2 * (cost of book) + 3 * (cost of notebook) = 18

2 * 6 + 3 * 2 = 18

12 + 6 = 18

18 = 18

The equation holds true, which confirms that our answer is correct.