Python:

In array X, replace the values greater than 5 with NaN.

Then, set the corresponding values in array Y = NaN to reflect the same NaN positions in array X.

original:

X= [2, 6, 7, 8, 9, 3, 4, 6]

Y = [1, 2, 3, 4, 5, 6, 7, 8]

final:

X= [2, nan, nan, nan, nan, 3, 4, nan]

Y = [1, nan, nan, nan, nan, 6, 7, nan]