Answer:
1170
Step-by-step explanation:
<em>hey there,</em>
(the other person just calculated each number themselves then added them up which i guess is okay but not in the long term for when you're taking a test for example or your teacher asks you this kind of question so it's better to memorize a formula.)
< There are two types of sequences: arithmetic and geometric. So also two formulas for finding sums of each. This situation is an arithmetic sequence.
Formula for the sum of an arithmetic sequence: 
We know there are 30 total rows so <em>n</em> = 30. <em>a1 </em>is the very first term of a sequence so this is 10 in this situation. Before we fill in the formula, we should find what <em>an</em> is equal to.
For this, we will use the basic formula you learned previously: 
<em>d</em> (the common difference) = a2-a1 = 12-10=2
<em>c </em>(the common ratio) = a1-d = 10-2 = 8
an = dn + c = 2(30) + 8 = 68
Now that we have found what a_n is equal to, we can plug everything into the sum equation.

So 1170 is your final answer. >
<u>Hope this helped! Feel free to ask anything else.</u>