Answer
$h=0.122~m$
Work Step by Step
The volume of additional water displaced by the man:
Density of sea water: $\rho=1030~kg/m^3$
$V={m\over\rho}={80~kg\over1030~kg/m^3}=0.078~m^3$
We can then use the volume to find the height of the volume of water displaced by the man standing on the can:
$r={0.9~m\over2}=0.45~m$
Volume of a cylinder:
$V=\pi r^2 h$
$h={V \over \pi r^2}={0.078~m^3\over\pi (0.45~m)^2}=0.122~m$
