1. The problem asks us to write the slope-intercept form of a line given the slope $m = -1$ and the y-intercept $b = 8$. 2. The slope-intercept form of a line is given by the formula: $$y = mx + b$$ where $m$ is the slope and $b$ is the y-intercept. 3. Substitute the given values into the formula: $$y = -1 \cdot x + 8$$ 4. Simplify the expression: $$y = -x + 8$$ 5. This is the equation of the line with slope $-1$ and y-intercept $8$ in slope-intercept form.