1. **State the problem:** Find the equation of the line passing through the points (-1, 3) and (-4, 3). 2. **Recall the formula for the slope of a line:** $$m = \frac{y_2 - y_1}{x_2 - x_1}$$ where $(x_1, y_1)$ and $(x_2, y_2)$ are the given points. 3. **Calculate the slope:** $$m = \frac{3 - 3}{-4 - (-1)} = \frac{0}{-4 + 1} = \frac{0}{-3} = 0$$ 4. **Interpret the slope:** A slope of 0 means the line is horizontal. 5. **Write the equation of a horizontal line:** Since the line passes through (-1, 3), the $y$-value is constant: $$y = 3$$ 6. **Final answer:** The equation of the line passing through (-1, 3) and (-4, 3) is $$y = 3$$ This matches the graph description of a horizontal line at $y=3$ between $x=-4$ and $x=-1$.