The answer is 5 because a^2 + b^2 = c^2
They are essentially asking us to solve:

Solving this equation for x tells us that it will take around 80.1 years for the materials in the vault to reduce to 357 pounds.
2304cubes(14^3 cm^3/cube)=6322176 cm^3
For calculating the mean, you want to add up all of the numbers then divide by how many numbers there are. So you'd do:
5+10+12+4+6+11+13+5 then divide that by 8
The answer to your question is: 8.25
110-8.75= 101.25. 101.25 divided by 9 = 11.25. Each pizza cost 11.25