How many {part of} are to/by {linear algebra} ?
How many parts make up linear algebra?
Linear algebra has how many parts?
SELECT ( COUNT ( ?l ) AS ?b ) { ?l property:part_of resource:linear_algebra }
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/P361> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> http://wikidata.dbpedia.org/resource/Q82571 .
} 

SELECT (COUNT(?sub) AS ?value ) { ?sub wdt:P361 wd:Q82571 }
8