Let's denote the number as x.

According to the problem, we have the equation:

x - 4 = 21 * (1/x)

To solve this equation, we can first multiply both sides by x to get rid of the fraction:

x^2 - 4x = 21

Then, we can rearrange the equation to make it a quadratic equation:

x^2 - 4x - 21 = 0

This equation can be factored into:

(x - 7)(x + 3) = 0

Setting each factor equal to zero gives the solutions x = 7 and x = -3.

However, the problem specifies that the number is positive, so the correct answer is 7.

Question

Let's denote the number as x.

According to the problem, we have the equation:

x - 4 = 21 * (1/x)

To solve this equation, we can first multiply both sides by x to get rid of the fraction:

x^2 - 4x = 21

Then, we can rearrange the equation to make it a quadratic equation:

x^2 - 4x - 21 = 0

This equation can be factored into:

(x - 7)(x + 3) = 0

Setting each factor equal to zero gives the solutions x = 7 and x = -3.

However, the problem specifies that the number is positive, so the correct answer is 7.

Knowee AI · Accepted Answer