How many {influenced by} are to/by {Gustave Courbet} ?
How many people are there that are influenced by Gustave Courbet?
How many are influenced by Gustave Courbet?
SELECT ( COUNT ( ?v ) AS ?x ) { ?v property:influenced_by resource:Gustave_Courbet }
SELECT (COUNT(?sub) AS ?subs ) {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> ?sub .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P737> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> http://wikidata.dbpedia.org/resource/Q34618 .
} 

SELECT (COUNT(?sub) AS ?value ) { ?sub wdt:P737 wd:Q34618 }
6