What is the answer and how do I get it

60

Step-by-step explanation:

for n=0, f(0+1) and f(1)=100

for n=1, f(1+1)=f(2) and f(2)=f(1)-8=100-8=92

for n=2, f(2+1)=f(3) and f(3)=f(2)-8=92-8=84

for n=3, f(3+1)=f(4) and f(4)=f(3)-8=84-8=76

for n=4, f(4+1)=f(5) and f(5)=f(4)-8=76-8=68

for n=5, f(5+1)=f(6) and f(6)=f(5)-8=68-8=60