(-4z=20) i got 16 by dividing 20 by negative 4 and getting z=16

-4z/-4=20/-4
z=-5
by dividing you should get -5

-4z= 20
to get z alone, divide both sides by -4

-4z/-4= 20/-4

-4 on the left cancels out; divide 20 by -4

the answer will also be negative since 20 is positive and you need two negatives to make a positive

z= -5

CHECK:
(-4)(-5)= 20
20= 20

ANSWER: z= -5

Hope this helps! :)