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.
Answer:
FALSEEEEE Teellll me if its right
Step-by-step explanation:
To divide by a fraction, multiply by the reciprocal of that fraction.
1/3 • 5/1 or 1/3 • 5
Calculate the product straight across.
1/3 • 5/1 = 5/3
Answer:
84°
Step-by-step explanation:
I know that the other angle (not x) is 48 because the lengths are the same of 2 sides. Therefore I can use 180-48-48 to get 84, the correct answer.