W varies directly as x,y,and z. If w=36 when x=2, y=8, and z=12 find w when x=1 y= 2, and z=4

W = kxyz

for the given values
36 = k(2)(8)(12)
k = 36/192 = 3/16

W = 3xyz/16
then
W = 3(1)(2)(4)/16 = 24/16 = 3/2