Astretched spring has a length of 12 inches when a weight of 2 lbs is attached to the spring. the same spring has a length of 18 inches when a weight of 5 lbs is attached to the spring. what is the length of the spring when no weights are attached?

The way I figured this one out was saying that if it takes 2lbs to stretch it to 12 inches and 5lbs to stretch to 18 inches that means that 3 additional pounds = 6 inches. Therefore, each additional pound is 2 inches. We know already that with 2 lbs it was 12 inches in length and we can also say that 2 lbs = 4 inches. So subtract 4 from 12 and you end up with the answer of 8 inches.