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.
The answer is x=-7 and x=-1
Answer:
c
Step-by-step explanation:

Answer:
1
Step-by-step explanation:
Ok, so the third and fourth don't seem right. I am going to assume it's either 1 or 2. Sorry if you get it wrong because of me.