Question

Лена задумала число. Если это число увеличить в 3 раза, а потом уменьшить на 10, то получится число, вдвое больше задуманного. Какое Число задумала Лена?

Answer 1

Ответ:

Пусть х задуманное число

2 * (3 * х - 10) = х;

6 * х - 20 = х;

6 * х - х = 20;

х * (6 - 1) = 20;

х * 5 = 20 

х = 20 : 5

х = 4 — задуманное число.

Ответ: число 4.

Answer 2

х*3-10=х*2

3х-10=2х

3х-10-2х=0

х-10=0

х=10

Лена задумала число 10

Answer 3

Problem Analysis

Lena has thought of a number. If she increases this number by 3 times and then decreases it by 10, the result is a number that is twice as large as the number she originally thought of. We need to determine the number Lena had in mind.

Solution

Let's assume the number Lena had in mind is x.

According to the problem statement, if Lena increases the number by 3 times, she would get 3x. Then, if she decreases it by 10, the result would be 3x - 10.

The problem also states that this result is twice as large as the number Lena originally thought of. So, we can set up the equation:

3x - 10 = 2x

Now, let's solve this equation to find the value of x.

Solving the Equation

To solve the equation, we'll isolate the variable x on one side of the equation.

3x - 10 = 2x

Subtracting 2x from both sides:

3x - 2x - 10 = 0

Simplifying:

x - 10 = 0

Adding 10 to both sides:

x = 10

Therefore, the number Lena had in mind is 10.

Conclusion

Lena had the number 10 in mind.