Answer:
10
Step-by-step explanation:
We want to find k when y=kx
2y = 20x
Divide each side by 2
2y/2 =20x/2
y = 10x
The constant of proportionality is 10
"inversely proportional," please.
z = k/x
When x is 3, z = 6; find k: 6 = k/3, or k = 18.
Then z = 18/x. When x = 12, z = 18/12 = 2/3 (answer)
Answer:

Step-by-step explanation:
2(x^2 + 10x + 25) + 3
2x^2 + 20x + 50 + 3
2x^2 + 20x + 53