How many {solved by} are to/by {Leonhard Euler} ?
How much did Leonhard Euler solve?
how much was solved by leonhard euler?
SELECT ( COUNT ( ?p ) AS ?i ) { ?p property:solved_by resource:Leonhard_Euler }
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/P1136> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> http://wikidata.dbpedia.org/resource/Q7604 .
} 

SELECT (COUNT(?sub) AS ?value ) { ?sub wdt:P1136 wd:Q7604 }
7