For Question 16 you need to make the lowest number using 1, 2,3,4,5,6,7,8,9. Therefore, with each number in order of lowest to highest it is 123,456,789. for Q 17, 900 is missing. When you add the values 3,000+40+7 you get 3,047. Subtract that from 3,947, (3,947-3,047) and you get 900.