Number and Letter Patterns

The correct pattern is: AC, EG, IK, MO, QS, UW, YA.

Here, we can see that every two letters are interchanged among themselves to get new word.

So, the word SHUT can be written as HSTU.

123 = 1² + 2² + 3² = 1 + 4 + 9 = 14
235 = 2² + 3² + 5² = 4 + 9 + 25 = 38
Similarly, 291 = 2² + 9² + 1² = 4 + 81 + 1 = 86

The word S represents 19, I represents 9, L represents 12, E represents 5, N represents 14 and T represents 20.

Hence, on combining all the numbers, we get the result as: 1991251420.

The number 13528 can be written as: 10,000 + 3000 + 500 + 20 + 8.

Hence, the number '3' is at thousand's place.