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:
7
Step-by-step explanation:
In similar triangles, corresponding elements are proportional. Then we get,
(2x + 1)/(x-1) = 10/4
4(2x +1) = 10(x-1)
8x + 4 = 10x - 10
8x = 10x - 14
2x = 14
x = 7
Hope it helps and if it does, please mark me brainliest...
360°/60°=6
in 360° you have 6 rotations of 60°
Maybe rewrite it simpler?