Correct Answer - Option 4 : 7(56)8
The logic here is
1) 9(79)7 → (9 × 7) + (9 + 7) = 63 + 16 = 79 = 79 (middle number)
2) 6(41)5 → (6 × 5) + (6 + 5) = 30 + 11 = 41 = 41 (middle number)
3) 9(69)6 → (9 × 6) + (9 + 6) = 54 + 15 = 69 = 69 (middle number)
4) 7(56)8 → (7 × 8) + (7 + 8) = 56 + 15 = 71 ≠ 56 (not middle number)
Hence, the correct answer is "7(56)8".