SOLUTION: Wich sequence follows the rule 3n-2,where n represents the position of a term in the sequence? A. 21,18,15,12,9,... B. 3,6,9,12,15,... C.1,7,10,13,16,... D. 1,4,7,10,13,...

To get term #1, plug in a 1 for n in the rule 3n-2

 3n-2
3(1)-2
  3-2
   1

So the answer can't be A or B because neither of those
begins with 1.  So the answer is either C or D.

To get term #2, plug in a 2 for n in the rule 3n-2

 3n-2
3(2)-2
  6-2
   4

So the answer is D.

But as a check, let's show that we get all 
the other numbers of D.

To get term #3, plug in a 3 for n in the rule 3n-2

 3n-2
3(3)-2
  9-2
   7

The next term of D is 7.

To get term #4, plug in a 4 for n in the rule 3n-2

 3n-2
3(4)-2
 12-2
  10

The next term of D is 10.

To get term #5, plug in a 5 for n in the rule 3n-2

 3n-2
3(5)-2
 15-2
  13

The next term of D is 13.

So we have proved that D is the only possible answer.

Edwin