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Work Shown:
old side length = 2x
new side length = 2*(old side length) = 2*2x = 4x
For any cube, the length, width and height are all the same. So L = W = H.
volume = L*W*H
volume = L*L*L
volume = L^3
volume = (4x)^3
volume = 4^3*x^3
volume = 64x^3