Question 1: write an equation for a line that is parallel to the y-axis?
Here is its graph which is the green line below:
It goes through 4 on the x-axis so its equation is x=4
Question 2: what is the x-intercept for the line whose equation you wrote?
That's the point (4,0)
Question 2 What is the y-intercept for the line whose equation you wrote?
There is none because parallel lines never intersect.
Edwin