Her total should be 84. You have your 30 dollars that will not change which you need to add to the amount of every visit. To find the amount for each time she went you have to do 3*18 because she went 18 times for 3 dollars each. Your answer to 3*18 should be 54. You now have to add those 54 to the 30 per month. 30+54. That should be 84
A way you can show work is just not use the commas then subtract then put the commas in when you're done. And, if the bigger number isn't as big or has as many numbers behind the decimal as the first one, add a zero at the end.
