Answer:
$8.25
Step-by-step explanation:
If she gets the bill each month, we need to calculate the monthly interest rate as follows
18%/12 = 1.5%
Because 18% is the annual rate and a year has 12 months.
Then, the interest charge will be 1.5% of the amount, so
$550 x 1.5% = $550 x 1.5 / 100 = $8.25
Therefore, the interest will be $8.25