5 is the initial distance away from home. To confirm this, one would plug in "0" for t (the distance away from home after 0 seconds, aka the initial distance) and get y = 5.
It's N=9 it's really confusing but trust me it N
The sum of a series is calculated with the following formula:
n/2(2a+(n-1)d) where n is the number of terms, a is the first term and d is the difference between the terms.
so for this series:
n/2(2*64+(n-1)*-2)=0
n(130-2n)=0
n=0 (not valid because n<1) n=65
so the 65th term gives the sum 0
Plug in 8 for g(8) to get 8(2) + 1 which is equal to 17, plug in 7 for f(x) to get 10-7 which is equal to 3. 17 + 3 is equal to 20 which means g(8) + f(7)= 20