The sun is v kilometers from the upper edge of the earth's atmosphere and q kilometers from the surface of the earth. which of the following expressions always represents the distance between the earth’s surface and the upper edge of the earth's atmosphere?

The distance between the Earth's surface and the upper edge of the Earth's atmosphere would be Q - V.

The distance from the Sun to the Earth is Q. The distance from the Sun to the upper edge of the atmosphere is V. If you subtract V from Q, the remaining distance is that of the Earth's atmosphere.  Q - V = the atmosphere

The expressions would be 0.25a