In the equation \( C = 18 + 4x \), the variable \( C \) represents the total cost, and \( x \) represents the number of books.
The term "4x" indicates that for each additional book Tatiana purchases, she spends an additional $4. Therefore, the coefficient \( 4 \) indicates the cost per book.
Statement #1: "Tatiana spent $4.00 per book at the public library."
This statement is correct as it accurately describes the coefficient of \( x \) in the equation.
Statement #2: "Tatiana spent $18.00 per book at the public library."
This statement is incorrect because $18 represents a fixed starting cost (or initial cost), not the cost per book.
Thus, Statement #1 could be a correct interpretation of the coefficient of a term.