The ages of two persons differ by 30 years. If 5 years ago, the elder one was 3 times as old as the younger one, then the present age of the younger person is:

Explanation

Let the present age of the younger person be x years. Then, the present age of the elder person will be x + 30 years (since their ages differ by 30 years). Step 1: Set up the equation based on the information from 5 years ago Five years ago, the age of the younger person was x - 5, and the age of the elder person was (x + 30) - 5 = x + 25. According to the problem, 5 years ago, the elder one was 3 times as old as the younger one: x + 25 = 3(x - 5) Step 2: Solve for x Expand and simplify the equation: x + 25 = 3x - 15 Rearrange to bring terms involving x to one side: 25 + 15 = 3x - x 40 = 2x Divide both sides by 2: x = 20 Answer: The present age of the younger person is 20 years.