## Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

The n th term can be calculated as: $a_n=a_1+d\times(n-1)$ Here: $a_n=210$ and we have to find $n$. In an arithmetic sequence, first we have to find the common difference, which can be calculated as the difference of any two subsequent terms: $d=a_2-a_1=18-10=8$. By substituting we get: $210=10+8\times(n-1)$ $n-1=\frac{210-10}{8}=25$ $n=26$