We know that 1 foot is 12 inches then, we change all quantities to inches to ease the calculations: 5 ft 9 in = 5(12) + 9 = 60 + 9 = 69 inches 10 ft 11 in = 10(12) + 11 = 120 + 11 = 131 inches so we add: <span>5 ft 9 in + 10 ft 11 in = 69 inches + 131 inches = 200 inches if we want the result in foot we divide: = 200/12 = 100/6 = 50/3 = 16 ft 8 in</span>