Answer: x = 139-c is used to replace and there are 87 child's ticket.
Explanation:
Let the number of child's ticket be 'c'.
Total number of people attended the game = 169
Let the number of adult's ticket be 'x'.
Cost of each child's ticket = $3.
Cost of each adult ticket = $5.
Total amount collected = $521
So, According to question, it must be look like this :
3c+5x=$521
Here, we need to replace x , so that a single variable equation can be written and solved to determine the number of child's tickets sold.
x+c=139
x=139-c
So, our single variable equation becomes
3c+5(139-c)=$521
3c+695-5c=521
-2c=521-695
-2c=-174
Hence, x = 139-c is used to replace and there are 87 child's ticket.