`36.121 -33.429 = "____"`.

Explanation

To solve the problem \( 36.121 - 33.429 \), we will follow these steps:

### Step 1: Align the numbers
First, we need to align the numbers by their decimal points:

```
36.121
- 33.429
```

### Step 2: Subtract the numbers starting from the rightmost digit
We will subtract each column starting from the rightmost side (the thousandths place).

1. **Thousandths place**: \( 1 - 9 \)
- Since 1 is smaller than 9, we need to borrow from the next column. The 2 in the hundredths place becomes 1, and the 1 becomes 11.
- Now, \( 11 - 9 = 2 \).

2. **Hundredths place**: \( 1 - 2 \)
- Again, we need to borrow from the next column. The 1 in the tenths place becomes 0, and the 1 becomes 11.
- Now, \( 11 - 2 = 9 \).

3. **Tenths place**: \( 0 - 4 \)
- We need to borrow again. The 6 in the units place becomes 5, and the 0 becomes 10.
- Now, \( 10 - 4 = 6 \).

4. **Units place**: \( 5 - 3 = 2 \).

5. **Tens place**: \( 3 - 3 = 0 \).

### Step 3: Write down the result
Now we can combine all the results from each column:

```
36.121
- 33.429
---------
2.692
```

Thus, the difference \( 36.121 - 33.429 = 2.692 \).

### Final Answer
The required difference is \( 2.692 \).

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