In one week (7 days), Mark eats 7 egg sandwiches, which is 1,750 calories. Subtract the total amount of calories he consumed by the number of calories consumed through egg sandwiches; 5,250-1,750=3,500. 3,500 is the total number of calories Mark consumed through eating one Big Burger everyday for 7 days. Divide 3,500 by 7 = 500. There are 500 calories in one Big Burger.