Final answer:
To find the number of hardcover books sold, solve the equation 0.75(x + 42,000) = 60,000. The number of hardcover books sold is 38,000.
Step-by-step explanation:
To find the number of hardcover books that were sold, we need to solve the equation 0.75(x + 42,000) = 60,000.
First, distribute the 0.75 to both terms inside the parentheses: 0.75x + 0.75(42,000) = 60,000.
Simplify the equation: 0.75x + 31,500 = 60,000.
Next, subtract 31,500 from both sides of the equation: 0.75x = 28,500.
Finally, divide both sides of the equation by 0.75: x = 38,000.
Therefore, there were 38,000 hardcover books sold.