Answer
The number of opossums killed in the fourth month is 30.
The total killed in the first four months is 68.
Work Step by Step
For the sequence with general term $a_{n} = (n+1)(n+2)$, where $n$ is the number of the month
The number of opossums killed in the fourth month (n = 4) is,
$a_{4}$ = $(4+1)(4+2)$ = $5 \cdot 6$ = 30.
and, the total killed in the first four months is
= $a_{1}$ + $a_{2}$ + $a_{3}$ + $a_{4}$
= $(2 \times 3)$ + $(3 \times 4)$ + $(4 \times 5)$ + $(5 \times 6)$
= $6 + 12 + 20 + 30$
= $68$