Question

Купили 5одинаковых простых карандашей и 7 одинаковых блокнотов. за всю покупку заплатили 50р. сколько стоит 1 простоц карандаш и один блокнот, если все блокноты на 20 р. дороже, чем все карандаши

Answer 1

Х-стоит карандаш
у-стоит блокнот
5х+7у=50
7у-5х=20
7у=50-5х
7у=20+5х
50-5х=20+5х
-5х-5х=20-50
-10х=-30
х=30/10=3 р-стоит карандаш
7у=20+5*3
7у=20+15
7у=35
у=35/7=5р-стоит блокнот

Answer 2

Пусть х - карандаши , тогда ( х +20 ) -блокноты
х+(х+20)=50
х+х+20=50
2х=30
х=15-карандаши
15+20=35 блокноты
ответ:15;35

Answer 3

Calculation of the Cost of One Pencil and One Notebook

To calculate the cost of one pencil and one notebook, we need to use the information provided in the question.

Let's assume that the cost of one pencil is represented by x and the cost of one notebook is represented by y.

Given that 5 identical pencils and 7 identical notebooks were purchased for a total of 50 rubles, we can set up the following equation:

5x + 7y = 50

Additionally, we are told that all the notebooks are 20 rubles more expensive than all the pencils. This can be represented as:

y = x + 20

Now we can solve these equations to find the values of x and y.

Substituting the value of y from the second equation into the first equation, we get:

5x + 7(x + 20) = 50

Simplifying the equation:

5x + 7x + 140 = 50

Combining like terms:

12x + 140 = 50

Subtracting 140 from both sides:

12x = -90

Dividing both sides by 12:

x = -7.5

Now that we have the value of x, we can substitute it back into the second equation to find the value of y:

y = -7.5 + 20 y = 12.5

Therefore, the cost of one pencil is -7.5 rubles and the cost of one notebook is 12.5 rubles.

Please note that the negative value for the cost of the pencil is not realistic. It is possible that there was an error in the given information or in the calculations.