How many {lake inflows} are to/by {Missouri River} ?
How much lake inflows to the Missouri River?
SELECT (COUNT(?sub) AS ?value ) { ?sub wdt:P200 wd:Q5419 }
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/P200> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> http://wikidata.dbpedia.org/resource/Q5419 .
} 

Missouri River has how much inflow?