Question

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

Answer 1

У брата х
у сестры х+4
всего 28
х+х+4=28
2х+4=28
2х=28-4
2х=24
х=12
ответ у брата 12, у сестры 16

Answer 2

1)28-4 24(отк.)было у брата и сестры без 4 открыток
2)24:2=12(отк.)было у брата
3)12+4 =16(отк.)было у сестры
Ответ:У брата-12отк.у сестры-16открыток

Answer 3

Problem Analysis

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

Solution

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

According to the given information, the total number of cards is 28: x + y = 28 The sister gives 4 cards to the brother, so the sister has y - 4 cards and the brother has x + 4 cards.

After the exchange, they have an equal number of cards: x + 4 = y - 4

Simplifying the equation, we get: x - y = -8 Now we have a system of two equations: x + y = 28 x - y = -8

We can solve this system of equations using the method of substitution or elimination.

Let's solve it using the method of elimination:

Adding the two equations together, we get: 2x = 20

Dividing both sides by 2, we find: x = 10

Substituting the value of x into one of the original equations, we can find y: 10 + y = 28 y = 18

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

Answer

The brother initially had 10 greeting cards and the sister initially had 18 greeting cards.

Explanation

Initially, the brother had 10 cards and the sister had 18 cards. The sister gave 4 cards to the brother, so the sister now has 18 - 4 = 14 cards, and the brother now has 10 + 4 = 14 cards. Therefore, they both have an equal number of cards, which is 14.