Question 274823
The average (arithmetic mean) number of students in 3 economics classes at a certain college is 24. If the total number of students in 2 of the classes combined is 38, how many students are in the remaining class? 
A 19 b 24 c 31 d 34 

Let x be the number of students in the remaining class. Then we have:

(38 + x)/3 = 24 

Solve for x.