The linear function g(x) = -4.5x + 144 represents the amount of money, g(x), Sara has on her lunch card, where x represents the number of days
since the beginning of each month. Which represents the amount of
money on Sara's lunch card at the beginning of each month?

Sara has $144 at the beginning of the month.

Step-by-step explanation:

At the beginning of the month, x = 0 because no days have passed since the beginning of the month. When x = 0, g(0) = -4.5(0) + 144 = 144, therefore, we know that Sara has $144 on her card at the beginning of the month.