Idon't get this at all could someone explain this?

The volume of gas a balloon can hold varies directly as the cube of its radius. imagine a balloon with a radius of 3 inches can hold 81 cubic inches of gas. how many cubic inches of gas must be released to reduce the radius down to 2 inches?

If x+y+z=0 what is the value of [tex] {x}^{3} + {y}^{3} + {z}^{3} [/tex]

Nellie is analyzing a quadratic function f(x) and a linear function g(x). will they intersect? f(x) g(x) graph of the function f of x equals one half times x squared, plus 2 x g(x) 1 5 2 10 3 15