  To date, the weak-phase $\gamma$ has been measured using two-body $B$-meson
decays such as $B\to D K$ and $B\to D\pi$, whose amplitudes contain only
tree-level diagrams. But $\gamma$ can also be extracted from three-body
charmless hadronic $B$ decays. Since the amplitudes for such decays contain
both tree- and loop-level diagrams, $\gamma$ obtained in this way is sensitive
to new physics that can enter into these loops. The comparison of the values of
$\gamma$ extracted using tree-level and loop-level methods is therefore an
excellent test for new physics. In this talk, we will show how U-spin and
flavor-SU(3) symmetries can be used to develop methods for extracting $\gamma$
from $B\to K\pi\pi$ and $B\to KK{\bar K}$ decays. We describe a successful
implementation of the flavor-SU(3) symmetry method applied to BaBar data.
