Correct Answer - Option 4 :
56 : 9
The logic is:
Reminder is 3 when first number in the pair is divided by the second number as follows:
1) 75 : 9 → 75 ÷ 9 → Remainder is 3
2) 45 : 6 → 45 ÷ 6 → Remainder is 3
3) 51 : 8 → 51 ÷ 8 → Remainder is 3
4) 56 : 9 → 56 ÷ 9 → Remainder is 2
Hence, 56 : 9 is the correct answer.