Answer
See below.
Work Step by Step
a) The nth term of an arithmetic sequence can be obtained by the following formula: $a_n=a_1+(n-1)d$, where $a_1=34.5+0.3=34.8$ is the first term and $d=-0.3$ is the common difference, thus $a_n=34.8+(n-1)(-0.3)=35.1-0.3n$
b) Using the formula and that $n=2020-1964=56$, $a_n=35.1-0.3\cdot56=35.1-16.8=18.3$
