1. An arithmetic sequence has a common difference of $-6$. If the 5th term, $a_5$, is 21, what is the 6th term, $a_6$? The 6th term is ___.
2. An arithmetic sequence has a first term of $a_1 = -10$ and a common difference of $d=3$. What is the value of the second term, $a_2$?
3. What is the next term in the arithmetic sequence $3, 11, 19, \dots$? The next term is ___.
4. What is the next term in the arithmetic sequence $\frac{1}{3}, 1, \frac{5}{3}, \dots$?
5. The 10th term of an arithmetic sequence is $a_{10} = -8$ and the common difference is $d=5$. What is the 11th term, $a_{11}$? The 11th term is ___.
6. An arithmetic sequence has a first term $a_1=8$ and a common difference $d=3$. What is the value of the $15^{\text{th}}$ term, $a_{15}$? The value is ___.
7. Consider the arithmetic sequence $5, 11, 17, \dots$. What is the $21^{\text{st}}$ term of this sequence?
8. What is the $30^{\text{th}}$ term of the arithmetic sequence that begins with $12, 8, 4, \dots$? The term is ___.
9. What is the $13^{\text{th}}$ term of the arithmetic sequence that begins with $\frac{1}{3}, 1, \frac{5}{3}, \dots$?
10. In the formula $a_n = a_1 + (n-1)d$, what does the expression $(n-1)$ represent in the context of an arithmetic sequence?