Answer:

Step-by-step explanation:
For this case we need a line parallel to the plane x z and yz. And by definition of parallel we see that the intersection between the xz and yz plane is the z axis. And we can take the following unitary vector to construct the parametric equations:

Or any factor of u but for simplicity let's take the unitary vector.
Then the parametric equations are given by:



Where the point given 
And then since we have everything we can replace like this:




Answer:
x=12.36 or 12 9/25 or 309/25
Step-by-step explanation:
Add up all the rainfall amounts and divide by 11
Answer:
I will use "complete-the-square" approach if thats ok
first 0.5(x - 2)² - 2
second -2(x - 4)² + 8