Final answer:
The constant of proportionality is $0.30 and the equation that relates the number of bagels, x, to the cost, y, is y = 0.30x.
Step-by-step explanation:
To find the constant of proportionality, we need to identify the relationship between the number of bagels and the cost. Looking at the table, we can see that as the number of bagels increases, the cost also increases. The cost increases by the same amount each time. For example, when the number of bagels increases by 1, the cost increases by $0.30. Therefore, the constant of proportionality is $0.30.
To fill in the equation that relates the number of bagels, x, to the cost, y, we can use the formula y = kx, where k is the constant of proportionality. In this case, the equation would be y = 0.30x.
Therefore, the correct answer is a) 0.30x