The area of the top face of a cube is 9 cm² use nine of these cubes to make a rectangular prism what is the volume of the rectangular prism

Does anyone know this? the andwer choices are: 79, 85, 101, and 135 degrees!

Achemist has 200 ml of a 10% sucrose solution. she adds x ml of a 40% sucrose solution. the percent concentration, y, of the final mixture is given by the rational function: the chemist needs the concentration of the final mixture to be 30%. how many milliliters of the 40% solution should she add to the 10% solution to get this concentration?

I'm confused on this could anyone me and show me what i need to do to solve it.