1. **Problem:** Find the equation of the line with slope 3 and y-intercept 9 in slope-intercept form. 2. **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. **Given:** Slope $m = 3$, y-intercept $b = 9$. 4. **Substitute:** Plugging values into the formula: $$y = 3x + 9$$ 5. **Answer:** The correct equation is $$y = 3x + 9$$ which corresponds to option د.