If you add 7 to a number and it equals 20, what is that number?

To find the unknown number, you can set up a simple equation based on the information given. The statement "If you add 7 to a number and it equals 20" can be represented as:

x + 7 = 20

Here, x represents the unknown number. To solve for x, you need to isolate it by subtracting 7 from both sides of the equation:

x + 7 - 7 = 20 - 7

x = 13

Thus, the number you are looking for is 13. This is why the answer you selected is correct—it directly follows from the mathematical operation performed to solve the equation.