Could i get help with my code? It says ufunc error

$3\mathrm{.}2[4$ pt$]$ Given the vectors, $u=[2,-10,4],v=[3,4,15],$ and $w=[-2,1,x],$ find the value of $x$ such that they are linearly dependent. If instead, the vectors were $u=[2,z,4],v=[3,4,15],$ and $w=[-2,1,2],$ find the value of $z$ such they are linearly dependent. Store the values of $x$ and $z$ in the variables $x$ and $z.$

$[39]$: import numpy as np

$u=np.$ array $([2,-10,4])$

$v=np.$ array $([3,4,15])$

$,$ None