Step-by-step explanation:

Answer:
A=z
B=-2
C=0
D=30
Step-by-step explanation:
First lets simply the equation
21 - (2x +3)2 + 4(1-1) + z^3
21 - (2x^2 + 9) + 4(0) + z ^3
21 - 2x^2 + 9 + z^3
- 2x^2 + z ^3 + 30
This means that:
A=z
B=-2
C=0
D=30
A direct variation is a proportional equation. Such as:
For every 3 cookies, linda gets 1 glass of milk. The equation for this is y=3x where y is the glasses and x is the cookies. this is a direct variation. It also has a linear line. Linear means straight. Rate of change and slope are the exact same thing. They are the value of 'm' in y=mx+b
12, because 4 rows and 3 sections in each
4x3=12