In each graph, they give you a line.
For part A, they want you to use the <u>Distance Formula</u> which is:

(x2 is supposed to be x sub 2, but I can't put subheadings in the equation tool)
x1, x2, y1, and y2 are the coordinates of the endpoints of the segment.
For part B, they want you to use the <u>Midpoint Formula</u>, which is:

The coordinate pair you get from the Midpoint Formula is your midpoint.
Hope this helps! :)