What are lines drawn to connect opposite corners of any rectangle that have the same length

The perimeter of a stage is 116 feet. it is 17 feet wide. how long is it?

Math it's appreciated. (picture provided)

An object is translated by (x + 4, y - 2). if one point in the image has the coordinates (5, -3), what would be the coordinates of its pre-image? (9, -5) (1, -5) (9, -1) (1, -1)