To find the price per shirt, simply divide the total (combined) cost of the shirts by the amount of shirts
A.) $26.96 (cost of 6 shirts) ÷ 6 (shirts) = $4.49 per shirt
B.) $21.00 (cost of 5 shirts) ÷ (5 shirts) = $4.20 per shirt
C.) $28.50 (cost of 7 shirts) ÷ (7 shirts) = $4.07 per shirt
Comparing A, B, and C, the best buy would be C ($28.50 for 7 shirts)