Question

У брата и сестры вместе 28 открыток.Сестра отдала брату 4 открытки,и открыток у них стало поровну.Сколько открыток было у каждого из них первоначально?

Answer 1

У брата было 10 у сестры 18.
1) 28:2=14 (открыток) должно быть у каждого
2)14-4=10 (открыток) было у брата
3) 28-10=18 (открыток) у сестры

Answer 2

4:28=7 ОТКРЫТОК                                                                                               ответ    первоначально у них было 7 открыток

Answer 3

Problem Analysis

We are given that the brother and sister have a total of 28 postcards. The sister gives 4 postcards to the brother, and after that, they have an equal number of postcards. We need to determine how many postcards each of them had initially.

Solution

Let's assume that the brother initially had x postcards, and the sister initially had y postcards.

According to the given information, the total number of postcards is 28: x + y = 28. After the sister gives 4 postcards to the brother, they have an equal number of postcards: x + 4 = y - 4.

We can rewrite this equation as: x - y = -8.

Now we have a system of two equations with two variables: ``` x + y = 28 x - y = -8 ```

We can solve this system of equations to find the values of x and y.

Adding the two equations together, we get: ``` 2x = 20 ``` Dividing both sides by 2, we find: ``` x = 10 ```

Substituting the value of x back into the first equation, we find: ``` 10 + y = 28 ``` Simplifying, we find: ``` y = 18 ```

Therefore, the brother initially had 10 postcards, and the sister initially had 18 postcards.

Answer

The brother initially had 10 postcards, and the sister initially had 18 postcards.