Eighteen years ago he was three times her age; today he's twice hers
When the Timpkinses married eighteen years ago, Mr. Timpkins was exactly three times his wife's age. Today he's exactly twice her age. How old was Mrs. Timpkins on her wedding day?
Reveal the answer
18 years old. If her age on the wedding day was w, his was 3w; eighteen years later she's (w+18) and he's (3w+18), and 3w+18 = 2(w+18) gives w = 18. That makes her 36 and him 72 today. This is Puzzle No. 43, 'Mrs. Timpkins's Age,' from Henry Dudeney's 1917 Amusements in Mathematics.
— Henry Ernest Dudeney, Amusements in Mathematics — Puzzle No. 43, 1917