The correct 4-digit code is 9.To solve the puzzle, we need to solve the four equations:Q1: A + B = 7 , Q2: B + C = 0, Q3: C + D = 1 , Q4: D & C = 0.
To solve the puzzle, we need to solve the four equations:
Q1: A + B = 7
Q2: B + C =0
Q3: C + D = 1
Q4: D & C = 0
Q4 can be solved easily, since D & C = 0 means that D must be 0. This means that C = 1.
Q3 can now be solved: C + D = 1, so C = 1 and D = 0, so the equation becomes 1 + 0 = 1, which is true.
Q2 can now be solved: B + C =, but we already know that C = 1, so the equation becomes B + 1 =. We don't have enough information to solve for B, so we'll leave it blank for now.
Q1 can now be solved: A + B = 7, but we don't know the value of B, so we can't solve for A either. We'll leave Q1 blank for now as well.
Since we don't know the value of B, we can't solve for A either. However, we do know that A + B = 7 and that B + C =. This means that A + B + C = 7 + = 9.
We also know that C + D = 1 and that D = 0, so C = 1. This means that A + B + C + D = 7 + 9 + 1 + 0 = 17.
The correct 4-digit code is 9.