Miles has a square garden in his backyard. he decides to decrease the size of the garden by 1 foot on each side in order to make a gravel border. after he completes his gravel border, the area of the new garden is 25 feet2.

If you are asking what the original garden was, before the gravel border, you would have to know the sides of the current square.   Since all sides of a square are the same, and A=s²  25ft² = 5²   so each side of the new garden is 5 ft.  Since he took a foot off all the way around, you can draw a frame around the square that is one foot away from the square in all directions.  You will see that the original square was 7 x 7 (not 6 x 6 as you might think)  - see attachment