1. **State the problem:** We need to find the equation of a line with slope $-\frac{1}{2}$ and y-intercept at the point $(0,3)$. 2. **Recall the formula:** The slope-intercept form of a line is given by: $$y = mx + b$$ where $m$ is the slope and $b$ is the y-intercept. 3. **Identify the values:** Here, $m = -\frac{1}{2}$ and $b = 3$. 4. **Write the equation:** Substitute the values into the formula: $$y = -\frac{1}{2}x + 3$$ 5. **Interpretation:** This equation means the line crosses the y-axis at 3 and for every 2 units you move right along the x-axis, the y-value decreases by 1 unit. **Final answer:** $$y = -\frac{1}{2}x + 3$$