The equation for d would be 6.6666666666
First you an put it as a fraction 100/15
Next you divide 100 by 15 because to get 1 second you divide 15 by 15 because that is the seconds. If you divide the denominater by 15 you have to do that to the numerator, therefor you would divide 100 by 15 and get 6.66666666
Hope this Helps!!!