This is a hopelessly vague question, Graeme. Answering questions requires the use of all aspects of written English-- grammar and structure, vocabulary, composition, style-- as well as the ability to read and understand, and the knowledge to formulate a correct answer to the question.
I have never seen worksheets or exercises on answering questions-- students usually get enough practice by, well, answering questions.
Do you have any more specific concerns about this that you could articulate?