A 12' x 15' rectangular swimming pool has a 3 foot wide nonslip surface around it what is the outer perimeter of the no slip surface

Since the surface is 3 feet wide around the pool add 6 feet to both dimensions (3 feet x 2 = 6).

12 ft + 6 ft. = 18 feet

15 ft + 6ft. = 21 feet

Perimeter = 2L + 2W

Perimeter = 2 (18) + 2 (21)

Perimeter = 36 + 42

Perimeter = 78 feet.