PREFIX dc: <http://purl.org/dc/elements/1.1/>
PREFIX ns: <http://example.org/ns#>
SELECT ?title ( ?p AS ?fullPrice ) ( ( ?fullPrice * ( "1"^^<http://www.w3.org/2001/XMLSchema#integer> - ?discount ) ) AS ?customerPrice ) WHERE {
  ?x ns:price ?p .
  ?x dc:title ?title .
  ?x ns:discount ?discount .
}