Answer:

Step-by-step explanation:
To solve this problem you must apply the proccedure shown below:
1. You need to apply the Distributive property on the left member of the equation:

2. Now, you must solve for
, as following:

Their error is that they divided 12 by 30, instead of 30 by 12 in order to get the price per pair
the correct unit price is $2.50 per pair
2.5 * 12 = 30
The circumference = π x the diameter of the circle (Pi multiplied by the diameter of the circle). Simply divide the circumference by π and you will have the length of the diameter. The diameter is just the radius times two, so divide the diameter by two and you will have the radius of the circle
If she maintains her average amount of movies bought every week, then she will buy 20 DVDs in 10 weeks. Explanation: she buys 4 every week, so if we want to find out how many are in 10 weeks, we must multiply two until we get to 10 ( five weeks ) then multiply that buy her average of movies. And that is how we get the answer of 20 DVDs! ( her at least I did )
Anyways, hope this helps!