Final answer:
Greg can spend $18.52 on items before sales tax to make sure the total with an 8% tax does not exceed $20. This makes the correct answer option (a).
Step-by-step explanation:
To determine how much Greg can spend on items including an 8% sales tax with $20, we need to calculate the total cost of items before tax that would amount to $20 once tax is added. To do this, we first convert the 8% sales tax to a decimal, which is 0.08. Then, we add 1 to this decimal to account for the original cost of the items (1 + 0.08 = 1.08). Next, we divide the total amount Greg has by this sum to find the maximum he can spend before tax.
$20 รท 1.08 = $18.52
Therefore, Greg can spend $18.52 on items before tax to have a total including tax of $20. This corresponds to option (a).