Answer
See below.
Work Step by Step
b) The sum of the first $n$ terms of an arithmetic sequence can be obtained by the following formula: $\frac{n(a_1+a_n)}{2},$ where $a_1$ is the first term, $a_n$ is the nth term and $n$ is the number of terms.
Hence here: $d=-1,a_1=30,a_{16}=15,n=16$
Hence here the sum: $\frac{n(a_1+a_n)}{2}=\frac{16(30+15)}{2}=360$
