Final answer:
The equation of the line with a slope of -1 and a y-intercept of -20 is y = -x - 20.
Step-by-step explanation:
The equation of a line in slope-intercept form is y = mx + b, where m is the slope and b is the y-intercept.
In this case, the slope is -1 and the y-intercept is -20.
Therefore, the equation of the line is y = -1x - 20, or y = -x - 20.
Learn more about Writing the equation of a line in slope-intercept form