6. The teacher gave this pattern to the class: the first term is 5 and the rule is add 4, subtract 1. Each student says one number. The first student says 5. Victor Is tenth in line. What number should Victor say? (lesson 5.6)​

Answer:
 D.  21
Step-by-step explanation:
The first terms are ...
 5, 9, 8, 12, ...
Each even-numbered term is 3 more than the previous even-numbered term. Then the even-numbered terms are ...
  n = 2, 4, 6, 8, 10
 an = 9, 12, 15, 18, 21
Victor should say "21."