###Human: A public official wants to donate 5 new soccer balls per each class in two schools. Each school has 4 elementary school classes and 5 middle school classes.  How many soccer balls would the public official donate in all?, ### Assistant: Each school has 4 + 5 = 9 classes.
So, there are a total of 9 x 2 = 18 classes for the 2 schools.
Therefore, the public official donates a total of 18 x 5 = 90 soccer balls. 
 So the answer is :  90