why in math, whenever you do an explanation, for example, 2x - 20, the subtraction sign make the 20 a negative number?

The negative sign is put before numbers to make them negative, or make their signs the opposite of what the are.

You have a 20.

+ 20

You don't need to put the + there if there is nothing before it, but that is a positive 20.

If you put a negative in front of it;

- (+ 20) = - 20

If you have a negative in front of parenthesis;

50 - (2x - 20)

50 - 2x + 20

70 - 2x

This means that the domain of this situation is , that is, you can talk between 0 and 200 minutes in the month.

Step-by-step explanation:

Ace Telecommunications charges $0.12 per minute of phone use plus a monthly service fee of $8.00 for the phone service.

This means that the cost of speaking for m minutes is given by:

You can talk for no more than 200 minutes in a month.

This means that:

What is the domain of this situation?

The domain of a function is the input variable.

In function C(m), m is the input variable, and since you can talk for no more than 200 minutes in a month, the restriction for the input is .

This means that the domain of this situation is , that is, you can talk between 0 and 200 minutes in the month.