Answer: 20 <= x <= 80.
- A 20 <= x <= 80
- B 20 <= x <= 100
- C 0 <= x <= 80
- D 20 <= x <= 75
Correct answer: A. 20 <= x <= 80
Explanation: Two conditions: (1) x ≥ 20. (2) Selling price = x+0.25x = 1.25x ≤ 100, so x ≤ 100/1.25 = 80. Intersection of both: 20 ≤ x ≤ 80. Answer: 20 ≤ x ≤ 80
One-variable inequalities use open (excluded) or closed (included) circles on a number line; two-variable inequalities use a dashed (strict) or solid (non-strict) boundary line, with the solution being the entire shaded half-plane on one side of it.
Concept context
Solving linear inequalities in one and two variables algebraically and graphically, and representing solutions on a number line or as a region in a plane.