Answer:

Given sequences are as follows:

Sequence 1: _ A D A C B _ _ B D C C
Sequence 2: 1 3 _ _ 1 2 4 2 _ _ _ _
Sequence 3: a _ _ b _ _ c d ? ? ? ?

We need to find the missing letters/numerals.

Finding the missing letters/numerals:

To find the missing letters/numerals, we need to observe the given sequences carefully and look for any pattern or relation between them. Let's analyze each sequence:

Sequence 1:

- The first letter is missing, but we can see that the second letter is 'A' and the third letter is 'D'. So, the missing first letter should be 'C'.
- The fourth letter is 'A', which is followed by 'C' and 'B'. Then, we have two missing letters. Looking at the pattern, we can observe that the sequence is alternating between the letters 'A', 'C', and 'B'. So, the missing letters should be 'A' and 'C'.
- After the missing letters, we have 'B', 'D', 'C', and 'C'. So, no letter is missing in this part.

Therefore, the missing letters in Sequence 1 are C, A, C.

Sequence 2:

- The first two numbers are missing, but we can see that the third number is 3 and the fourth number is 1. So, the missing first two numbers should be 2 and 4.
- After the missing numbers, we have '2', which is followed by a missing number and then '4'. Looking at the pattern, we can observe that the sequence is alternating between the numbers '1' and '2'. So, the missing number should be '1'.
- After that, we have '2', which is followed by two missing numbers. Looking at the pattern, we can observe that the sequence is alternating between the numbers '1', '2', and '4'. So, the missing numbers should be '1' and '4'.
- Finally, we have three missing numbers. Looking at the pattern, we can observe that the sequence is repeating the same pattern of numbers '1', '2', and '4'. So, the missing numbers should be '1', '2', and '4'.

Therefore, the missing numbers in Sequence 2 are 2, 4, 1, 1, 4, 1, 2, 4.

Sequence 3:

- The first letter is missing, but we can see that the second letter is 'a'. So, the missing first letter should be 'c'.
- After the missing letter, we have two missing letters. Looking at the pattern, we can observe that the sequence is alternating between the letters 'a', 'b', 'c', and 'd'. So, the missing letters should be 'b' and 'c'.
- After that, we have three missing letters. Looking at the pattern, we can observe that the sequence is repeating the same pattern of letters 'd', 'd', 'c'. So, the missing letters should be 'd', 'd', 'c'.

Therefore, the missing letters in Sequence 3 are c, b, c, d, d, c.

Hence, the complete sequences are:

Sequence 1: C A D A C B