Part A is 6 and the bottom one is "Take a line and connect it from point C to the middle of A and B then put another line connecting to D to the middle of A and B"
Answer:
29.7 is the standard deviation :)

The graph is attached below.
In order to find the y-intercept, check the graph and see where it hits the y-axis, so in this case the y-intercept would be at (0,6).
To find the x-intercept, check the graph and see where it hits the x-axis, and here it hits at x = -6.