Answer
$w=3w_1+w_2-2/3w_3$
Work Step by Step
Let $av_1+bv_2+cv_3=(2,4,1)$. Then $a-b=2$, $2a+3c=4$, $b=1$.
Thus if $b=1$, then $a-b=2\\a-1=2\\a=3$.
Then
$2a+3c=4\\2(3)+3c=4\\-2=3c\\c=-2/3$
Thus
$w=3w_1+w_2-2/3w_3\\(2,4,1)=3(1,2,0)+(-1,0,1)-2/3(0,3,0)$
