Answer
$\displaystyle -\frac{1}{3}d$
Work Step by Step
A loss is something we subtract, something negative.
$\displaystyle \frac{1}{3}$ of (something) is written as $\displaystyle \frac{1}{3}\cdot$(something),
so "$\displaystyle \frac{1}{3}$ of d" is $\displaystyle \frac{1}{3}\cdot d$
Expression:$\displaystyle \quad -\frac{1}{3}d$
