What are the coordinates for H" and I'

Which property is illustrated by the following statement? if hxa rgi, then rgi hxa.

How to do this , and can some one explain

When keisha installed a fence along the 200 foot perimeter of her rectangular back yard, she left an opening for a gate. in the diagram below, she used x to represent the length in feet of the gate? what is the value? a. 10 b. 20 c. 25 d. 30