Let's analyze and solve the missing digits problem step by step.

Problem A:

We have the following equation:

  _ _ 3
+ 4 6 _
-------
  1 3 7

From this, let's fill in the missing digits.

1. The last column is already complete:

   • $3 + \_ = 7$. So the missing digit in the last position must be 4 because $3 + 4 = 7$.

2. Moving to the middle column:

   • $6 + \_ = 3$, but we have a carry of 1 from the previous column (because $13 - 6 = 7$).
   • Therefore, $6 + \_ + 1 = 13 \implies \_ = 6$. The middle digit in the first row is 5.

3. Now, for the first column:

   • $4 + \_ = 1$, but there's no carry from the middle column.
   • This means the number must be 5 because $4 + 5 = 9$, and we carry a 1 over.

So, the completed solution for part A is:

  5 5 3
+ 4 6 4
-------
  1 3 7

Problem B:

The second problem is:

  _ 0 5 7
+ 1 1 _ 4
---------
  2 3 3 4
---------
  6 _ 4 _

Let’s solve this:

1. The last column:

   • $7 + 4 = 11$, so the last digit must be 1, with a carry of 1.

2. Third column:

   • $5 + \_ + 1 = 14$, which gives the missing digit as 8.

3. Second column:

   • $0 + 1 = 1$, but considering the carry from the next column, it sums to 13, so the missing digit must be 3 to satisfy the sum.

4. First column:

   • $1 + \_ = 6$, so the missing digit in the first row is 5.

The completed solution for part B is:

  5 0 5 7
+ 1 1 8 4
---------
  6 3 3 4

Summary:

• A:

  5 5 3
  

• 4 6 4

1 3 7

- **B:**

5 0 5 7

• 1 1 8 4

6 3 3 4

Do you have any questions or would you like further clarification?

Here are 5 related problems for practice:
1. Solve for missing digits in:  
 $$\_ \ 6 \ 2 \ + \ 3 \ \_ \ 5 \ = \ 5 \ 7 \ \_$$
2. Find the missing digits for:  
 $$\_ \ 7 \ 8 \ + \ 4 \ \_ \ \_ \ = \ 1 \ 1 \ 3 \ 5$$
3. Solve for the missing number in:  
 $$\ 4 \ \_ \ 2 \ + \ 3 \ \ 5 \ = \ 7 \ \_$$
4. Solve this digit puzzle:  
 $$\_ \ 9 \ 3 \ + \ 6 \ \_ \ = \ 8 \ 4 \ \_$$
5. Find the unknown digits:  
 $$\_ \ \_ \ 7 \ + \ 5 \ 3 \ \_ \ = \ 9 \ 0 \ 8$$

### Tip: 
When solving digit puzzles, always start from the right-most column and consider any possible carries carefully.