To find out how much each bag of potatoes costs, let's first define the variables involved in the problem.
Let \( x \) represent the cost of one bag of potatoes.
Isabella buys 3 bags of potatoes, so the total cost for the potatoes would be \( 3x \).
According to the problem, she pays a total of $21.40 for both the milk and the potatoes. She pays $3.73 for the milk.
The equation to represent this situation is:
\[
3x + 3.73 = 21.40
\]
Now, we can solve for \( x \):
1. Subtract the cost of the milk from the total:
\[
3x = 21.40 - 3.73
\]
\[
3x = 17.67
\]
2. Divide both sides by 3 to find the cost of one bag of potatoes:
\[
x = \frac{17.67}{3}
\]
\[
x = 5.89
\]
Thus, each bag of potatoes costs **$5.89**.