f(n+1) = f(n) - 8
f(1) = 100
try with n = 1
f(1+1) = f(1) - 8
f(2) = 100 - 8
f(2) = 92
try with n = 0
f(0+1) = f(0) - 8
f(1) = f(0) - 8
100 = f(0) - 8
100 + 8 = f(0) -8 + 8
108 = f(0)
so we know that
f(0) = 108
f(1) = 100
f(2) = 92
the bigger function you have, you need to -8
so
f(3) = 84
f(4) = 76
f(5) = 68
f(6) = 60
so f(6) = 60
