The slope-intercept form of a line is shown below:
y = mx + b
Where
m is the slope
b is the y-intercept
We can find the slope of the given line:
y = -20
When comparing with the given form, but we need to complete this equation first as follows:
y = 0x - 20
Note we have completed the term with the 'x' with a zero coefficient.
Now we can compare, the two parameters are:
slope = 0 (zero)
y-intercept = -20