1. **State the problem:** We need to find the equation of a line with slope $m=3$ that passes through the point $(-2,-15)$ in slope-intercept form $y=mx+b$. 2. **Recall the slope-intercept form:** The equation of a line is given by $$y=mx+b$$ where $m$ is the slope and $b$ is the y-intercept. 3. **Use the point to find $b$:** Substitute $m=3$, $x=-2$, and $y=-15$ into the equation: $$-15=3(-2)+b$$ 4. **Simplify and solve for $b$:** $$-15 = -6 + b$$ Add 6 to both sides: $$-15 + 6 = b$$ $$b = -9$$ 5. **Write the final equation:** $$y=3x - 9$$ This is the equation of the line in slope-intercept form.