Arthimatic and combining in 3D Arrays Numpy

Question

let\'s say I have a 3D array x:

x = np.arange(0, 24).reshape(4, 3, 2)

output: 
array([[[ 0,  1],
    [ 2,  3],
    [ 4,  5]],

   [[ 6,  7],
    [ 8,  9],