What's the value of (-8)(2/3)

The depth of a lake at a certain point, wich is a function of the distance of that point from shore, is 30 feet.

If 30 lb of rice and 30 lb of potatoes cost ? $27.60? , and 20 lb of rice and 12 lb of potatoes cost ? $15.04? , how much will 10 lb of rice and 50 lb of potatoes? cost?

Factor the polynomial expression x6 – x3 – 20