Answer
12.6 mL
Work Step by Step
According to Boyle's law,
$V=\frac{c}{P}$ where $c$ is the proportionality constant that depends on temperature and amount of gas.
$\implies c=VP=10.0\,mL\times1.2\,bar=12\,mL\,bar$
Since the temperature and the amount of gas is constant, we can use the value of $c$ obtained to get the volume at 0.95 bar pressure.
$V=\frac{c}{P}=\frac{12\,mL\,bar}{0.95\,bar}=12.6\,mL$
