Fill in the blanks!

Let's fill in the blanks based on simplifying the given expressions:

1. To simplify \( \frac{1}{X^{50}} \), we can express it as \( X^{-50} \). So, the first blank would be **X**:
- Simplified: **X** / X^(50) = X^(-50)

2. We want to get an expression that can subtract with \( 1/r^{4} \). The most straightforward way is to express it as \( r^{-4} \). So, the second blank would be **r**:
- **1/r^{4} - 1/r**

3. For \( r^{(-4)} - s^{(-1)} \), it appears we already have a form which suggests we may not need to fill anything in, as both terms are negative exponents. So nothing is needed for this one:
- r^(-4) - s^(-1) (No blanks to fill)

4. In the case of \( \frac{3v^{7}}{u^{12}} \), this can also be expressed as \( 3v^{7}u^{-12} \), matching the form given. So, we confirm:
- 3v^(7) / u^(12) = **3v^{7}u^{-12}** (already given in the last expression)

In summary:
1. First Blank: **X**
2. Second Blank: **r**
3. No blanks for the third one.
4. Confirming the fourth one fits without needing any additional input.

Let me know if you have more questions or need further help!