What are the language and title of the ordered books with price less than 20% of the average price of all ordered books?
language refers to language_name; books with price less than 20% of the average price refers to price < Multiply (AVG(price), 0.2)
SELECT DISTINCT T3.language_name, T2.title FROM order_line AS T1 INNER JOIN book AS T2 ON T1.book_id = T2.book_id INNER JOIN book_language AS T3 ON T3.language_id = T2.language_id WHERE T1.price * 100 < ( SELECT AVG(price) FROM order_line ) * 20