[Speaking of computers] But they are useless. They can only give you answers.

As discussed in this entry from Quote Investigator, the origin seems to be the article "Pablo Picasso: A Composite Interview" by William Fifield which appeared in The Paris Review 32, Summer-Fall 1964, and collected a number of interviews Fifield had done with Picasso.

Common later variant: "Computers are useless. They can only give you answers." This variant seems to have arisen in the 1980s, the earliest known appearance in a book is Herman Feshbach, "Reflections on the Microprocessor Revolution: A Physicist's Viewpoint", in Man and Technology (1983), ed. Bruce M. Adkins, where the attribution is described as "rumoured".<!-- | Before 1990: in a dozen books. Over the next decade, in a dozen quiz-books and chapter header-quotes, always without source. Since 2000, it has spread virally through all kinds of media. | books.google.com advanced search results | 1983: 2 books | 1984-90: 9 books | 1991-2000: 80 books -->