Answer:
z = 2
Step-by-step explanation:
The proportionality can be written as ...
x = ky/z
Then ...
z = ky/x
If x is constant, z is directly proportional to y. When y is reduced by a factor of 2 from 6 to 3, then z will be reduced by a factor of 2 from 4 to 2.
z = 2 . . . . when y=3 and x=3
