How fat is you plz I need to know

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?

How many times larger is 9 × 10^8 than 3 × 10^-5? a. 3 × 10^13 b. 3 × 10^-40 c. 3 × 10^-13 d. 3 × 10^3

What is the value of x in the equation 1/5x - 2/3y = 30 , when y = 15