  Explicit expressions for magnetoresistance $R$ of planar and layered strongly
inhomogeneous two-phase systems are obtained, using exact dual transformation,
connecting effective conductivities of in-plane isotropic two-phase systems
with and without magnetic field. These expressions allow to describe the
magnetoresistance of various inhomogeneous media at arbitrary concentrations
$x$ and magnetic fields $H$. All expressions show large linear
magnetoresistance effect with different dependencies on the phase
concentrations. The corresponding plots of the $x$- and $H$-dependencies of
$R(x,H)$ are represented for various values, respectively, of magnetic field
and concentrations at some values of inhomogeneity parameter. The obtained
results show a remarkable similarity with the existing experimental data on
linear magnetoresistance in silver chalcogenides $Ag_{2+\delta}Se.$ A possible
physical explanation of this similarity is proposed. It is shown that the
random, stripe type, structures of inhomogeneities are the most suitable for a
fabrication of magnetic sensors and a storage of information at room
temperatures.
