How many {participant} are to/by {Nursultan Nazarbayev} ?
Which is the number of the participants that Nursultan Nazarbayev have?
How many participants did Nursultan Nazarbayev have?
SELECT ( COUNT ( ?x ) AS ?l ) { ?x property:participant resource:Nursultan_Nazarbayev }
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/P710> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> http://wikidata.dbpedia.org/resource/Q57394 .
} 

SELECT (COUNT(?sub) AS ?value ) { ?sub wdt:P710 wd:Q57394 }
5