unit cost = price ÷ amount purchased
in the first case, Sam paid $6.75 for 2.5 pounds of meat
in his case, we divide $6.75 by 2.5 pounds, which yields $2.70 per pound
in the second case, Alicia paid $7.50 for 2.5 pounds of meat
so, we divide $7.50 by 2.5 pounds, which yields $3.00 per pound