We pick c.root-servers.net, one of the 13 root servers (1), and ask it about 7.1.7.5.7.7.b.c.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.1.a.c.d.0.1.0.0.2.ip6.arpa and learn that ip6.arpa is delegated to six name servers (2), so we ask b.ip6-servers.arpa where we learn that d.0.1.0.0.2.ip6.arpa is delegated to six name servers, including sec1.authdns.ripe.net (3), so we ask that one and get the following answer:
Authoritative answer
AUTHORITATIVE for 7.1.7.5.7.7.b.c.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.1.a.c.d.0.1.0.0.2.ip6.arpa.