Answer
$2.1cm$
Work Step by Step
We know that
$\rho_{Hg}V_{submerged}=\rho_{lead}V$
$\rho_{Hg}(\frac{\pi d^2x}{4})=\rho_{lead}(\frac{\pi d^2h}{4})$
$\implies x=(\frac{\rho_{lead}}{\rho_{Hg}})h$
We plug in the known values to obtain:
$x=\frac{11.3\times 10^3}{13.6\times 10^3}(2.5)=2.1cm$