Harriet needs to ship a small vase. The box she will use has a volume of 216 cubic inches. if the side lengths are all the same, what is the length of each side of the box?

I'm at a bookstore with $\$35$ in my pocket and a $20\%$-off coupon. what is the cost of the most expensive book i can buy with my money and the coupon? (assume that there are books of every possible price in the bookstore. it's a large bookstore! )