Because of a lack of rainfall two years ago, the water level in a local reservoir fell 12 1/2 feet. last year, the water level rose 5 3/4 feet. by how many feet did the water level of the reservoir change overall during these two years?

Initially, the water level changed from normal level then decreased, 12.5 feet. From this level to the next year, the water level changed by an increase of 5.75 feet. Two changes occurred, first a decrease of 12.5 feet, second an increase of 5.75 feet. If overall implies addition of the two, then 18.25 feet changed in two years.