  Magnetization plateaus are some of the most striking manifestations of
frustration in low-dimensional spin systems. We present numerical studies of
magnetization plateaus in the fascinating spin-1/2 skewed ladder system
obtained by alternately fusing five- and seven-membered rings. This system
exhibits three significant plateaus at $m = 1/4$, $1/2$ and $3/4$, consistent
with the Oshikawa-Yamanaka-Affleck condition. Our numerical as well as
perturbative analysis shows that the ground state can be approximated by three
weakly coupled singlet dimers and two free spins, in the absence of a magnetic
field. With increasing applied magnetic field, the dimers progressively become
triplets with large energy gaps to excited states, giving rise to stable
magnetization plateaus. Finite-temperature studies show that $m=1/4$ and $1/2$
plateaus are robust and survive thermal fluctuations while the $m=3/4$ plateau
shrinks rapidly due to thermal noise. The cusps at the ends of a plateau follow
the algebraic square-root dependence on $B$.
