* Literally: The sun and moon are celestial bodies. You can't add them together in a mathematical sense.

* Symbolically: The sun and moon are often seen as opposites (day and night, light and dark). So, they could represent a balance, a duality, or even a complete whole.

* Astrologically: In some cultures, the sun and moon represent masculine and feminine energies. Combining them could symbolize harmony or a powerful force.

So, what does sun plus moon equal? It depends on how you interpret the question!