二、 1 . The sum of the first 15 terms of an arithmetic sequence is 225, find the 8th term.
二、1, Solve $\because 15 \mathrm{a}_{1}+\frac{15 \times 14}{2} \mathrm{~d}=225$, i.e., $15\left(a_{1}+7 d\right)=225, \quad \therefore a_{3}=a_{1}+7 d=\frac{225}{15}=15$.