straightforward vs unchallenging

straightforward

adj
  • easy, simple, uncomplicated, without difficulty 

  • proceeding in a straight course or manner; not deviating 

  • direct; forthright; frank; sincere 

adv
  • In a straightforward manner; straightforwards; straightforwardly. 

unchallenging

adj
  • Not challenging; easy to do. 

How often have the words straightforward and unchallenging occurred in a corpus of books? (source: Google Ngram Viewer )