[25, 25, 50, 50, 100] the return will be "NO" cause the ticket price is 25 and after selling 4 you have no $25 bill left So How you can return $75 to the buyer..

For that test you can't give change for the 100 dollars bill with two 50 dollars bills.

Either reading the logs or the error message wrong. The log appears above the test result and 'NO' should equal 'YES' means your function returned 'NO' instead of the expected 'YES'.

This is the test and you can see it expects 'YES' test.assert_equals(tickets([25, 25, 25, 100]), "YES")