Answer: the system of equations that represents this situation are
12x + 6y = 180
x = 2y
Step-by-step explanation:
Let x represent the number of hardcover books that were sold in a day.
Let y represent the number of paperback books that were sold in a day.
The discount bookstore sells hardcover books for $12 and paperback books for $6. The total sales that day were $180. It means that
12x + 6y = 180
The number of hardcover books sold that day was twice the number of paperback books. It means that
x = 2y
