Answer:
Parallel lines always have the same slope.
Explanation:
If we use the example you gave, y = x - 10, the slope of the line is 1. We just have to find another line with a slope of 1. It doesn't matter what the y-intercept is, the slope just has to be the same. Some examples of parallel lines to y = x-10 are y = x, y = x + 5, or y = x - 5. Hope this helps!