Tickets to a concert cost $2 for children and $5 for adults. if 630 people attended the concert and the ticket sales totaled $2,910, how many children attended the concert?

To answer the question, let x be the number of children who went to the concert and y the number of adults. The equations that would best illustrate the descriptions are,
                              x + y = 630
                             2x + 5y = 2910
Solving for x and y gives an answer of x = 80 and y = 550. Therefore, 80 children went to the said concert. 

Let us assume the number of children attending the concert = x
Let us assume the number of adults attending the concert = y
Then
x + y = 630
y = 630 - x
2x + 5y = 2910
Now let us put put the value of y from the first equation to the second equation, we get
2x + 5y = 2910
2x + 5(630 - x) = 2910
2x + 3150 - 5x = 2910
- 3x = 2910 - 3150
- 3x = - 240
x = 240/3
   = 80
From the above deduction, we can conclude that the number of children attending the concert is 80.