The ratio of the price of a bag to the price of a book was 9:4.<br>During a sale, the prices of the bag and the book were reduced by $7 and $2 respectively.<br>The ratio of the price of the bag to the price of the book became 2 : 1.<hr>The bag cost $<input min="0" type="number" id ="imp6pg098q8_1" class="lineinput" placeholder="?" /> at first.