Create an equation to show how to solve this problem: Thomas rented 2 bicycles, which were late for return by 6 days. His fine for being late was 18$. How much was her charged per day per bike for being late?

Thomas rented 2 bicycles, which were late for return by 6 days. His fine for being late was 18$. If the fine for being late is count by multiplying the number of bicycles with the duration of the late, the answer would be:

fine = number of bicycle * duration of late

$18 = fine rate * 2 bicyles * 6 days

fine rate = (($18 / 2 bicyles) / 6 days) = $0.66 / bicycle days