Answer:
total cost = 10d +5.50
Explanation:
Hi, to answer this question we have to write an equation with the information given: 
So, the total cost is the sum of the shipping cost (5.50) and the product of the cost of each DVD (10) and the number of DVDs ordered (d) 
Mathematically speaking: 
Total cost = 10d +5.50 
Feel free to ask for more if needed or if you did not understand something.