Final answer:
To represent Marissa's situation as a linear equation, we can use y = 15x + 13.50, where y represents the total cost, x represents the number of trays of cookies, 15 represents the cost per tray, and 13.50 represents the base fee.
Step-by-step explanation:
To write a linear equation that represents Marissa's situation, we can use the equation y = mx + b, where y represents the total cost, x represents the number of trays of cookies, m represents the cost per tray, and b represents the base fee. Given that Marissa charges a base fee of $13.50 and $15 for each tray of cookies, we can write the linear equation as: y = 15x + 13.50. In this equation, the independent variable is x (the number of trays of cookies) and the dependent variable is y (the total cost). The y-intercept is 13.50, which represents the base fee, and the slope is 15, which represents the cost per tray of cookies.