Find the thirteenth term of an arithmetic sequence if the first term is 3 and the common difference is 3.

To solve this we are going to use the formula to find the nth term of an arithmetic sequence: 
where
is the neth term of the sequence 
is the first term of the sequence 
is the common difference 

We know fromm our problem that the first term of the arithmetic sequence is 3 and the common difference is 3, so  and . Lets replace those values in our formula:





Now, to find the thirteenth term of the sequence, we are going to replace  with 13:




We can conclude that the thirteenth term of the arithmetic sequence is 39