Which intercept? An x-intercept or a y-intercept?

If -20 is the y-intercept, then that's k. Slope-intercept form of the equation of the line is y = mx + b, and b is the y-intercept. So the equation is just

.

But if -20 is the x-intercept, then you plug in -20 for x and 0 for y:

So the equation would be

.

01