The answer for the blank space is the Multiplication Property of Equality.

Here’s why:

In the equation $-y = 4$, to rewrite $y$, you multiply both sides of the equation by $-1$, which transforms the equation into $y = 4$. The Multiplication Property of Equality allows you to multiply both sides of the equation by the same number (in this case, $-1$) to isolate the variable.

Would you like any further explanation, or do you have any additional questions?

Here are 5 related questions to expand this:

1. What is the Addition Property of Equality?
2. How does the Division Property of Equality work?
3. Why is isolating the variable important in solving equations?
4. Can you apply the Multiplication Property of Equality with fractions?
5. What are the steps to solving equations with variables on both sides?

Tip: When solving linear equations, always aim to isolate the variable step by step by applying inverse operations, such as adding, subtracting, multiplying, or dividing.