Puzzle for January 9, 2023  ( )

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Find the 6-digit number ABCDEF by solving the following equations:

eq.1) A + B + C + D + E + F = 18 eq.2) E = A - F eq.3) A = B - E eq.4) F = B + E eq.5) B = C - F eq.6) D - F = C + F

A, B, C, D, E, and F each represent a one-digit non-negative integer.

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Hint #1


In eq.2, substitute B - E for A (from eq.3), and (B + E) for F (from eq.4): E = B - E - (B + E) which becomes E = B - E - B - E which makes E = -2×E Add 2×E to both sides of the above equation: E + 2×E = -2×E + 2×E which makes 3×E = 0 which means E = 0


  

Hint #2


In eq.3, replace E with 0: A = B - 0 which makes A = B


  

Hint #3


In eq.4, replace E with 0: F = B + 0 which makes F = B


  

Hint #4


In eq.5, substitute B for F: B = C - B Add B to both sides of the equation above: B + B = C - B + B which makes 2×B = C


  

Hint #5


Substitute B for F, and 2×B for C in eq.6: D - B = 2×B + B which becomes D - B = 3×B Add B to each side of the above equation: D - B + B = 3×B + B which makes D = 4×B


  

Solution

Substitute B for A and F, 2×B for C, 4×B for D, and 0 for E in eq.1: B + B + 2×B + 4×B + 0 + B = 18 which simplifies to 9×B = 18 Divide both sides of the above equation by 9: 9×B ÷ 9 = 18 ÷ 9 which means B = 2 making A = F = B = 2 C = 2×B = 2 × 2 = 4 D = 4×B = 4 × 2 = 8 and ABCDEF = 224802