1. Draw a ray first, then intercept a long line segment on the ray with a compass, and then intercept a short line segment with the line segment already drawn inside as the endpoint, and the rest is to find the difference between the two line segments.

2. Draw a ray first, then cut a long line segment on the ray with a compass, and then cut a short line segment outward with one end of the drawn line segment as the endpoint. The longest line segment drawn is the sum of two lines.

Sketch.