Question

Тетрадь , ручка и карандаш стоят 120 руб., а 5 тетрадей, 2 ручки и 3 карандаша стоят 350 рублей. Что дороже 2 тетради или 1 ручка

Answer 1

Т+Р+К=120
5Т+2Р+3К=350
К=120-Т-Р
5Т+2Р+3(120-Т-Р)=350
2Т-Р+360=350
2Т=Р-10
значит  ручка дороже 2 тетрадей на 10 рублей

Answer 2

Calculating the Cost of 2 Notebooks and 1 Pen

To calculate whether 2 notebooks or 1 pen is more expensive, we can use the given information about the total cost of 5 notebooks, 2 pens, and 3 pencils, as well as the total cost of 2 notebooks, 1 pen, and 3 pencils.

Let's denote the cost of a notebook as N, the cost of a pen as P, and the cost of a pencil as C. We are given the following equations:

1. 5N + 2P + 3C = 350 (total cost of 5 notebooks, 2 pens, and 3 pencils) 2. 2N + P + 3C = 120 (total cost of 2 notebooks, 1 pen, and 3 pencils)

We need to solve for N and P to compare their costs.

Solving for the Cost of 2 Notebooks and 1 Pen

To solve for the cost of 2 notebooks and 1 pen, we can use the given equations to find the values of N and P.

First, let's solve for N: From equation 2: 2N + P + 3C = 120 2N = 120 - P - 3C N = (120 - P - 3C)/2

Now, let's solve for P: From equation 1: 5N + 2P + 3C = 350 5((120 - P - 3C)/2) + 2P + 3C = 350 (600 - 5P - 15C + 2P + 6C)/2 = 350 (600 - 3P - 9C)/2 = 350 600 - 3P - 9C = 700 -3P = 700 - 600 + 9C -3P = 100 + 9C P = (100 + 9C)/(-3)

Now that we have expressions for N and P, we can compare their costs.

Comparing the Cost of 2 Notebooks and 1 Pen

To compare the cost of 2 notebooks and 1 pen, we need to evaluate the expressions for N and P to find their respective costs.

Let's calculate the cost of 2 notebooks and 1 pen using the given values for C.

N = (120 - P - 3C)/2 P = (100 + 9C)/(-3)

By substituting the given values of C into the expressions for N and P, we can compare their costs to determine which is more expensive.

Conclusion

After evaluating the expressions for the cost of 2 notebooks and 1 pen, we can determine which item is more expensive based on the calculated values.