Answer: Number 11: About 48 feet of soil.
Number 12: Yes, 10 cubic feet of sand is more than enough to fill the sand box. The sand box is around 6 cubic feet so it will be plenty.
Step-by-step explanation: 11 is about 48 feet of soil because 8.5 times 8.5 times 2/3 is 48.1666. I'm going to assume you just need whole numbers.
11 is yes because 12 1/4 times 1/2 is 6.1, or just 6. Since the sand box is 6 cubic feet and you have 10 cubic feet of sand it will be enough.