Final answer:
The correct representation of the condition given is the inequality x ≥ 21, meaning any number greater than or equal to 21 satisfies the given condition.
Step-by-step explanation:
The equation representing the situation where five times a number added to 15 is at least 120 can be written as 5x + 15 ≥ 120. To solve for x, we subtract 15 from both sides of the inequality, resulting in 5x ≥ 105. Next, we divide both sides by 5 to get x ≥ 21. This means that the number x must be greater than or equal to 21 to satisfy the condition stated in the problem. Thus, the all possible values for x are represented by the inequality x ≥ 21.