Use the law of cosines to solve for side g.
g^2 = e^2 + f^2 - 2*e*f*cos(G)
g^2 = 10^2 + 8^2 - 2*10*8*cos(57)
g^2 = 76.85775 ... make sure your calc is in degree mode
g = sqrt(76.85775)
g = 8.766855
g = 8.8
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