C
the sum to infinity of a geometric series = 
where a is the first term and r the common ratio
=
= 81 × 3 = 243
Answer:
$2.20
Step-by-step explanation:
If you want to leave a 20% tip, multiply the cost by 0.20 to get the tip amount or multiply the cost by 1.20 to get the total including tip.
B (smallest two digit even number) = 10 <=== B
AB = 840
A = 840/B
A = 840/10
A = 84 <=== A
C - A = 816
C - 84 = 816
C = 816 + 84
C = 900 <===== C