The distance from the person to the mirror is 5 ft. The distance from the mirror to the giraffe is 15 ft.
15/5 = 3
Multiply the height of the person by 3:
5 ft = 60 inches 60+3 = 63 inches
63 x 3 = 189 inches
189/12 = 15.75 ft = 15 feet 9 inches
The giraffe is 15 ft 9 inches tall