Answer
20ml.
Work Step by Step
$HCl + AgNO_3 -> AgCl + HNO_3$
1. Because the proportion is 1:1, the number of moles of $HCl$ has to be the same of $AgNO_3$:
nº of moles($HCl$) = nº of moles($AgNO_3$)
2. We can find the number of moles by this formula:
$n = Concentration \times Volume$
$C(HCl) \times V(HCl) = C(AgNO_3) \times V(AgNO_3)$
$0.150 \times V(HCl) = 0.200 \times 0.015$
$V(HCl) = \frac{0.003}{0.15}$
$V(HCl) = 0.02L = 20ml$
