Answer:
137 hamburgers
Step-by-step explanation:
Let us call h the number of hamburgers sold and c the number of cheeseburgers.
Now we are told that a combined 411 hamburgers and cheeseburgers were sold, meaning

Furthermore, we are also told that two times as many cheeseburgers were sold as hamburgers, meaning

Now, the first step in finding the value of h is to substitute c = 2h in the first equation to get


Dividing both sides by 3 gives


which is our answer!
Hence, 137 hamburgers were sold.