Answer
$d_{2}$ = 2i + 4j
Work Step by Step
We are given
$d_{1}$ + $d_{2}$ = 5$d_{3}$
$d_{3}$ = 2i + 4j
We can use $d_{1}$ from part a to solve for $d_{2}$, where $d_{1}$ = 8i + 16j.
Plug unit vector notation of $d_{1}$ and $d_{3}$ into the first given equation
$d_{1}$ + $d_{2}$ = 5$d_{3}$
8i + 16j + $d_{2}$ = 10i + 20j
$d_{2}$ = 2i + 4j
