B, because to substitute for a variable you have to have an equation to substitute first.
You need to pay $40 to make your balance 0 and then another $40 to make it $40.
In all you will have to pay $80
Rational, whole, integer, sorry I’m not sure what a natural number is though
Answer:
C
Step-by-step explanation:
S(6)= -2(1-(-3)^6)/1-(-3)