D , because 28-9=21 and 21=x
You should add the picture so we can see
-7=z/2+1
What you first need to do is to multiply both sides of the equation by 2
-14=z+2
Now you move the variable to the left side and change within it’s own sign
-z-14=2
Into
-z=2+14
Now you then add the numbers
-z=16
The last part you do is change the sign on both sides in this equation
z=-16
Therefore, z=-16 is your answer in number 16.
