Final answer:
To find out how many lollipops Doug had when Marco had 6, we can set up a proportion based on the given ratio of 7:2. Cross-multiplying, we find that Doug had 21 lollipops.
Step-by-step explanation:
To find out how many lollipops Doug had, we need to set up a proportion based on the given ratio. The ratio of Doug to Marco's lollipops is 7:2. Since Marco had 6 lollipops, we can set up the proportion: 7/2 = x/6. Cross-multiplying, we get 2x = 7 * 6, which simplifies to 2x = 42. Dividing both sides by 2, we find that x, or the number of lollipops Doug had, is 21.