Answer:
189 Gallons
Explanation:
7 gallons for 3 classrooms, so 7/3 for 1 classroom
multiply 7/3 * 129 to get 301 gallons at North High School
multiply 7/3 * 48 to get 112 gallons at Edgewater Elementary
301 - 112 = 189 gallons more at North High School than at Edgewater Elementary