On Sunday, a local hamburger shop sold a combined total of 428 hamburgers and cheeseburgers. The number of cheese burgers sold was three times the number of hamburgers sold. How many hamburgers were sold on Sunday?

The equation you can use is x +3 x=428 with x as the number of cheeseburgers and 3 x the number of hamburgers you solve for x and get 4 x=428 and x=107 so 321 hamburgers were sold that day.