Question: If the present age of a grandfather is 80 years and the age of his grandson is 20 years, how many years ago was the grandfather 3 times as old as the grandson?
Options:
Correct Answer: 20
Solution:
Let x years ago, grandfather\'s age was 80 - x and grandson\'s age was 20 - x. We need 80 - x = 3(20 - x). Solving gives x = 10.