13.5% Let's just add up the areas. Left arm, front and back - 4.5% * 2 = 9% from elbow to fingertips. So only half of the left arm is burned. so 9%/2 = 4.5% Left chest and abdomen. Both the chest and abdomen are 9% each, but only half is burned. So (9+9)/2 = 9 So the total area burned is 4.5 + 9 = 13.5%