Simplify the following text for a Grade 8 native English-speaking person.
Original: The libretto , written by W. H. Auden and Chester Kallman , is based loosely on the eight paintings and engravings A Rake 's Progress ( 1733 -- 1735 ) of William Hogarth , which Stravinsky had seen on May 2 , 1947 , in a Chicago exhibition .
Simplified: The libretto written by W. H. Auden and Chester Kallman is based loosely on the eight paintings and engravings from the 18th century by William Hogarth called A Rake 's Progress . Stravinsky had seen these paintings in 1947 at an exhibition in Chicago .