Answer
Small: 0.076
Medium: 0.088
Large: 0.078
The small is the best buy.
Work Step by Step
The cost per square inch is found by dividing the cost by the area. Subtract 2 from the cost of the small pizza to account for the coupon.
Small: $(8-2)\div78.5=6\div78.5=0.076$
Medium: $10\div113.04=0.088$
Large: $12\div153.86=0.078$
The small is the best buy because it has the lowest cost per square inch.