First of all, this is a geometric series. First of all, let me tell you what a geometric series is: a geometric series refers to a series in which the ratio of each term to its previous term is equal to the same constant from the second term, usually expressed by G and P. This constant is called the common ratio of geometric series, usually expressed by the letter Q (q≠0), and the geometric series is a 1≠ 0. Where each item in {an} is not 0. Note: When q= 1, an is a constant series.

Secondly, this is a problem of finding the sum of the first n terms in geometric series. There is a formula to solve this problem. Let's look at its formula: the summation formula is described in words: Sn= the first term (the power of the common ratio 1- n)/(the common ratio ≠ 1) If the common ratio is q, we must pay attention to discussing whether the common ratio q is/when using the first n terms of geometric series for summation.

Now, let's look at the data of the corresponding formula in your question. Obviously, the first term of this geometric series is 5, the common ratio is 3, and the sum of the first six terms is obtained.

Finally, the data is substituted, and S6 = 5 (1-36)/(1-3) =1820.

I suggest you study the knowledge of geometric series, and it is best to know how its related formulas come from, so that you can easily solve this kind of problem or its deformation in the future.

I hope I can help you!