Explanation:

Let’s break this down step by step:

- The rules: swap ‘+’ with ‘—’ and swap every ‘6’ with ‘7’ (and vice-versa).

- Option 1:

Original: 67 - 76 + 43 = 100

Swap 6 and 7: 76 - 67 + 43

Swap + and —: 76 + 67 - 43

Evaluate: 76 + 67 = 143; 143 - 43 = 100

This works.

- Option 2:

Original: 76 - 75 + 77 = 56

Swap 6 and 7: 67 - 67 + 66 = 57

Swap + and —: 67 + 67 - 66

Evaluate: 67 + 67 = 134; 134 - 66 = 68

Doesn’t match right side.

- Option 3:

Original: 62 - 67 + 76 = 83

Swap 6 and 7: 72 - 76 + 67

Swap + and —: 72 + 76 - 67

Evaluate: 72 + 76 = 148; 148 - 67 = 81

Not equal to 83.

- Option 4:

Original: 78 - 68 + 66 = 59

Swap 6 and 7: 87 - 78 + 77

Swap + and —: 87 + 78 - 77

Evaluate: 87 + 78 = 165; 165 - 77 = 88

Not matching right side.

What this really means is:

Option 1 is the only one that checks out after the swaps and changes.