Frozen yogurt costs $0.50 per ounce so the cost for Alec's is 8.6 ounces * $0.50 per ounce which is $4.30. Kiara is 8.2 ounces * $0.50 per ounce which is $4.10. The total is $4.30+$4.10 which is $8.40.
8.6 plus 8.2 is 16.8 so they had a total of 16.8 ounces. $0.50 per ounce so you need to multiply 16.8 by 0.50 which is 8.40. you can also do 8.6(0.5) plus 8.2(0.5)= 4.3 plus 4.1 = 8.4
