A jazz concert brought in $124000 on the sale of 8,000 tickets. if the tickets sold $10& $20 each, how many of each type of ticket were sold?

If all were $10 tickets, the revenue would be $80,000. Actual revenue is $44,000 more than that amount. Replacing a $10 ticket with a $20 ticket adds $10 to the revenue, so there must have been $44,000/$10 = 4,400 such replacements.

4400 tickets were sold for $20

3600 tickets were sold for $10