Final answer:
To determine how much less a bottle of grapefruit juice costs at Store B compared to Store A, we calculate the cost per bottle at Store A to be $1.80 and use the given equation y = 1.7x to find that the cost per bottle at Store B is $1.70. Thus, Store B is $0.10 less expensive per bottle.
Step-by-step explanation:
To find out how much less a bottle of grapefruit juice costs at Store B compared to Store A, we first need to determine the cost per bottle at Store A. Since Lydia can buy 7 bottles for $12.60 at Store A, we divide the total cost by the number of bottles to get the cost per bottle:
Cost per bottle at Store A = Total cost at Store A / Number of bottles
Cost per bottle at Store A = $12.60 / 7 bottles
Cost per bottle at Store A = $1.80
Now, using the equation y = 1.7x for Store B, where y represents the total cost and x the number of bottles, we calculate the cost per bottle at Store B:
Since x represents 1 bottle, we can see that y = 1.7 × 1 which means the cost per bottle at Store B is $1.70.
To find the difference in cost per bottle between the two stores, we subtract the cost per bottle at Store B from the cost per bottle at Store A:
Difference in cost = Cost per bottle at Store A - Cost per bottle at Store B
Difference in cost = $1.80 - $1.70
Difference in cost = $0.10
So, a bottle of grapefruit juice is $0.10 less at Store B than at Store A.