You answer (166.50) is correct lol. You would first do 18 times 12.75 to get 229.5. That is how much money she would have WITHOUT parking. You will then do 18 divided by 3 which is 6. 6 is the number of times she is charged for parking. You then do 10.50 times 6 to get 63. 63 is how much she pays for parking a week. Lastly you do 229.5 minus 63 and get 166.5.