Answer:
Number of children, x= 400
Number of adults, y = 100
Step-by-step explanation:
Let the number of children be x
Let the number of  adults be y
Given : Total number of people, Â x + y = 500 Â --------(1)
      Total amount collected, 5x + 10y = 3000  ---------(2)
(1) => y = 500 - x
Substitute y in (2) : 5x + 10(500 - x) = 3000
               5x + 5000 - 10x = 3000
                -5x = 3000 - 5000
                 -5x = -2000
                  x = 400
Substitute x in (1) : 400 + y = 500
                   y = 500 - 400
                   y = 100