Answer
$x=9$
Work Step by Step
$(x-5)^{\frac{3}{2}}=8~~$ (Square both sides):
$[(x-5)^{\frac{3}{2}}]^2=8^2$
$(x-5)^3=64$
$x-5=\sqrt[3] {64}$
$x-5=4$
$x=9$
Check the solution:
$(9-5)^{\frac{3}{2}}=4^{\frac{3}{2}}=(\sqrt 4)^3=2^3=8$