The first term of a geometric series is 3, and the sun of the first term and the second term is 15 what is the sum of the first six terms

To solve this problem you must apply the proccedure shown below:
 1. You have the following information given in the problem above:
 - The first term of a geometric series is 3.
 - The sum of the first term and the second term is 15.
 2. Keeping this on mind, you must find the common ratio, as following:
 
 3. Now, multiply each term by the common ratio, and you will obtain:
 
 4. The sum of the first six terms is:
 
 The answer is: