In the pair JAM : 24 every letter is replaced by its place number counting A as 1, and the three numbers are added: 10 + 1 + 13 = 24. Complete the analogy: BOX : ?

B is 2nd, O is 15th and X is 24th, so the total is 2 + 15 + 24 = 41. The trap 40 comes from counting places backwards from Z, which makes B 25th, O 12th and X 3rd, giving 25 + 12 + 3 = 40. 39 comes from taking X as the 22nd letter instead of the 24th, giving 2 + 15 + 22. 17 is 2 + 15, with the last letter left out of the total.