NPR Weekend Edition Sunday Puzzle
August 25, 2019
Tyler Lipscomb
Presented by Will Shortz

If:
5 =4
6 = 9
7 = 5
What does 12 = ?

Answer:

12 = 55

When the numbers are spelled out, they contain Roman numerals:

5 = FIVE - Roman numeral IV (4)
6 = SIX - Roman numeral IX ( 9)
7 = SEVEN - Roman numeral V (5)
12 = TWELVE - Roman numeral LV (55)