Answer:
It was an increase of 200%.
Explanation:
In order to identfy the percent of the change we need to first find the absolute value, to do that we subtract the final value from the initial one. We have:
absolute difference = 36 - 12 = 24 inches
Since this value is positive it was an increase. Now we need to find the percentage at which it was increased, to do that we can use a rule of three in a way that the original value is 100% and the value we want to know is the percentage for the absolute increase. We do this as follows:
12 inches -> 100%
24 inches -> x %
12*x = 2400
x = 2400/12 = 200 %
It was an increase of 200%.