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%
