Hard to do or be done; arduous; perplexing.
Hard to influence or satisfy; intractable; exacting.
I will not exactly say difficult. – The Complete Project Gutenberg Works of George Meredith by George Meredith
These were questions difficult to answer. – Iermola by Joseph Ignatius Kraszewksi
I had no difficult decision to make. – Gossamer 1915 by George A. Birmingham