Lines m and n are parallel lines. if line m has a slope of -1, find the slope of line n.

-1

Step-by-step explanation:

Since they are parallel lines, they have the same slope.

You can see this visually by graphing two lines with the same slope and different y intercepts.

so, start with 1xxx. With various values of d, we get

d=1: 1234, 2345, 3456, 4567, 5678, 6789

d=2: 1357, 2468, 3579

d=3: 147? bzzt

Now, with negative d, we have

d=-1: 9876, 8765, 7654, 6543, 5432, 4321, 3210

d=-2: 9753, 8642, 7531, 6420

d=-3: 9630

So it should be 21