In order to answer the question, you have to know the formula of the volume of a sphere.
Volume = (4/3) pi r^3
Sphere 1 = (4/3) 3.14 3^3
Sphere 1 = 113.04 cm ^3
Sphere 2 = (4/3) 3.14 6^3
Sphere 2= 904.32 cm^3
Difference = Sphere 2 - Sphere 1
Difference = 904.32 - 113.04
Difference = 791.28 cm^3
The larger balloon has 791.28 cm^3 more water than the smaller one.
