2/10c + 12/6

Debra has a collection of toy cars that Weighs 12/6 grams. She is buying new cars, each car ways 2/10 Grams. Let the total weight of her collection be represented by W. Let the number of toy cars Bought be represented by c. Any equation that represents this scenario is: 2/10c + 12/6. What is the total weight of her collection if she buys 18 cars?