Answer:
107 hamburgers
Explanation:
Let's call hamburgers A and cheese burgers B.
We know that A + B = 321
And that the number of cheeseburgers sold was two times the number of hamburgers sold which means -> B = 2A
So A + 2A = 321
3A = 321
Now you need to divide both sides of the equation by 3 and you get:
A= 107