There are 6 apples and 2 oranges. So the ratio of apples to oranges would be 6:2. However this can be simplified, because these number have a common factor, which is 2. So you divide 2 by 2, and 6 by 2, and get 1 and 3. So the ratio of apples to oranges in simplified form is 1:3. Hope this explains it :)
