How many {edibility} are to/by {edible mushroom} ?
How many mushrooms are not poisonous to humans?
How many mushrooms are edible?
SELECT ( COUNT ( ?h ) AS ?e ) { ?h property:edibility resource:edible_mushroom }
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/P789> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> http://wikidata.dbpedia.org/resource/Q654236 .
} 

SELECT (COUNT(?sub) AS ?value ) { ?sub wdt:P789 wd:Q654236 }
300