To solve for $b$ in the equation $y = mx + b$, follow these steps:

1. Start with the given equation: $y = mx + b$

2. To isolate $b$, subtract $mx$ from both sides of the equation: $y - mx = b$

So, the correct answer is: $b = y - mx$

This corresponds to the second option in the image.

Would you like more details on this solution or have any other questions? Here are some related questions you might find useful:

1. How do you solve for $x$ in the equation $y = mx + b$?
2. What is the slope-intercept form of a linear equation?
3. How does the value of $b$ affect the graph of a linear equation?
4. Can $m$ and $b$ be negative in a linear equation? What would that mean graphically?
5. What are some real-world examples where linear equations like $y = mx + b$ are used?

Tip: When isolating a variable, always perform the same operation on both sides of the equation to maintain equality.