What number minus one-half is equal to negative one half

Jim is painting the inside of a circular helicopter pad. how many cans of paint would he need if the pad is 50 feet across and each can of paint covers about 200 ft2.

Candy lives in the center of town. her friend darlene lives 28 miles to the east and her friend dana lives 21 miles north. approximately how far do dana and darline live apart ?

With both problems. a.s.a.p directions on photo ^