The delicatessen has 1,320" (110' · 12"/foot) of bread.
According to the given data, a 6" sandwich yields $0.80 profit, and a 10" sandwich yields $1.20 profit.
So, a 6" sandwich yields $0.133 profit per inch ($0.80 ÷ 6")
and a 10" sandwich yields $0.12 per inch ($1.20 ÷ 10")
In view of those figures, in order to maximize profit, the owner of the delicatessen should make ONLY 6" sandwiches. Any other combination will result in less profit.