Answer
You need $3$ mL.
Work Step by Step
RECALL:
$P=BR$ where $B$=base, $P$=part, and $R$= rate or percent
The given problem has:
$B=2000$ mL
$R=0.15\%$
Solve for $P$ using the formula above to obtain:
$P=BR
\\P=0.15\% \times 2000
\\P=0.0015 \times 2000
\\P=3 \text{ mL}$
Thus, you need $3$ mL.
