How many {item operated} are for {cook} ?
Which is the number of items that the cook can operate?
How many items can the cook operate?
SELECT ( COUNT ( ?r ) AS ?x ) { resource:cook property:item_operated ?r }
SELECT (COUNT(?obj) AS ?objs ) {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q156839> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P121> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> ?obj .
} 

SELECT (COUNT(?obj) AS ?value ) { wd:Q156839 wdt:P121 ?obj }
2