Pls help need help asap ! thanks

With this question! what is process of elimination? ? p. s. my brothers acc got banned so add his new one @ yamauchiyamyam17

F(n + 1) = f(n) – 8. if f(1) = 100, what is f(6)?

A3-dimensional figure has a square base and 4 lateral faces that meet at a point. explain the difference between the cross sections when a slice is made perpendicular to the base through the vertex, and when a slice is made perpendicular to the base and not through the vertex