we know that
An <u>arithmetic sequence</u> is a sequence of numbers such that the difference of any two successive members of the sequence is a constant. The constant is called common difference
In this problem we have an arithmetic sequence
The common difference is equal to
Let
a1--------> the first term of the pattern
<u>the pattern is equal to</u>
2x + 3*6 = 36
2x = 36-18
2x = 18
x = 9