Tips & Tricks Short trick∶ ⇒ 4 – 3 = 1 → 8 ∴ 4 + 3 = 7 → 8 × 7 = 56 years Detailed solution∶ Let the age of the first person be 3x. ⇒ The age of the second person = 4x ⇒ The difference in their ages = 4x – 3x ⇒ x = 8 ⇒ The sum of their ages = 3x + 4x = 7x = 56 years ∴ The sum of their ages is 56 years.