Answer:
The egg salad sandwich
Explanation:
The cheese sandwich is 1/4 lb for 6 inches. For it to be proportional, the 12 inch would be twice that amount (2/4 or 1/2 lb). But, the actual 12 inch cheese sandwich is 3/4 lbs.
The chicken salad sandwich is 3/4 lbs for 6 inches. For it to be proportional, the 12 inch would be twice that amount (6/4 or 3/2 lbs). But, the actual 12 inch chicken salad sandwich is 7/4 lbs.
The egg salad sandwich is 2/3 lbs for 6 inches. For it to be proportional, the 12 inch would be twice that amount (4/3 lbs). The 12 inch sandwich is 4/3 lbs, so it is proportional.
The vegetable sandwich is 3/4 lbs for 6 inches. For it to be proportional, the 12 inch would be twice that amount (6/4 or 3/2 lbs). But, the actual 12 inch vegetable sandwich is 5/4 lbs.