Brian buys 6 books and the total cost is $24.18. What is the constant of proportionality that relates the cost in dollars, y, to the number of books, x?

4.03

Step-by-step explanation:

Y = kx

y = 24.18

x = 6

k = constant of proportionality

Y = kx

Step 1. Substitute number based on the formula

24.18 = k6

Step 2. Transpose Y to the left to find the ratio of constant proportionality

K = 24.18/6

Step 3. Divide Y over X

K = 4.03 (answer)