Need help with parallel lines finding the value of x

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?

Which expression is equivalent to 3^3 + 2^2?

Someone answer this asap for the first five terms of a sequence are shown. 5, 11, 23, 47, 95, . . which recursive function defines the nth term in the sequence for n > 1? a. f(n) = f(n - 1) + 6 b) f(n) = f(n - 1) + 48 c) f(n) = 3 • f(n - 1) + 1 d) f(n) = 3 • f(n - 1) - 4