Chapter 14 - Sequences, Series, and the Binomial Theorem - 14.2 Arithmetic Sequences and Series - 14.2 Exercise Set - Page 902: 27

$n=28$

The n th term of an arithmetic sequence can be calculated as: $a_n=a_1+d\times(n-1)$ Here: $a_{n}=-76$, $a_1=5$, $d=-3$ and we have to find $n$. By substituting we get: $-76=5+(-3)\times(n-1)$ $n-1=\frac{-76-5}{-3}=27$ $n=28$