can anyone help me im stuck on this Eureka Math Grade 4 Module 5 Lesson 22 Homework im tryna help my daughter with her homework and i dont really understand this new math

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

Can someone me out here number 4 plz

Mr. brettler is hanging up a 5-foot tall rectangular welcome sign in the gym. he has drawn a sketch on a coordinate grid. he has the lower vertices of the sign at (9, –3) and (–6, –3). where would the upper vertices be on the grid?