Question: What is the height difference between Mount Everest and K2?
SPARQL:
PREFIX dbo: <http://dbpedia.org/ontology/>
PREFIX res: <http://dbpedia.org/resource/>
SELECT DISTINCT (?h1-?h2)
WHERE {
        res:Mount_Everest dbo:elevation ?h1 .
        res:K2 dbo:elevation ?h2 .
}