You plant a tree that is 36 inches tall. After one year, the tree is 43 inches tall. Which expression describes the percent of increase in the tree's height?

36 - 100%43 - x  %
we multiply by cross ->  36 * x = 100 / 43 
we should remove '100%' from new value, because we find only increase.. no new value in percent.
x + 100 = (43 * 100)/36 
x =  4300/36 - 100x = 119+ 16/36 -100x = 19 +4/9



the answer is 

19.44% increase