How many {decays to} are to/by {carbon-14} ?
How many times does carbon-14 decay?
SELECT (COUNT(?sub) AS ?value ) { ?sub wdt:P816 wd:Q840660 }
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/P816> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> http://wikidata.dbpedia.org/resource/Q840660 .
} 

Which is the number that carbon-14 can decay?