Let's analyze the image to find the equation of the straight line.

From the graph, we can identify two key aspects of the straight line:

1. Slope: The slope (m) of the line is the ratio of the change in $R$ to the change in $s$. Looking at the graph, we see that as $s$ increases by 6 (from 0 to 6), $R$ decreases by 9 (from 6 to -3). Thus, the slope is: $m = \frac{\Delta R}{\Delta s} = \frac{-9}{6} = -\frac{3}{2}$

2. Intercept: The intercept (where the line crosses the $R$-axis) is at $R = 6$, which gives us the y-intercept (c).

So, the equation of the line is: $R = -\frac{3}{2}s + 6$

Looking at the answer choices in the image, the correct answer is: $R = -\frac{3}{2}s + 6$

Do you have any questions, or would you like more details on this?

Here are some related questions for further exploration:

1. How do you calculate the slope of a line from a graph?
2. What is the significance of the y-intercept in a linear equation?
3. Can the slope of a line ever be positive? What would that look like on a graph?
4. How do you rewrite the equation of a line if you are given different points?
5. What is the general form of a linear equation in two variables?

Tip: To easily find the slope of a line, pick two clear points on the graph, and use the formula $\frac{\text{change in y}}{\text{change in x}}$.