The screen shot does not display. But, we may be able to help resolve this without the screen shot.
If you have created the decision tree, and it returns either Yes or No, go back to the connectors coming out of the decision shape and confirm the "Result" you are checking for matches the results of the decision tree (see page 28 of the exercise guide).
What are the available calculations? On the Declare Expression form, click the double-headed arrow to access the available calculations:
You should see these available calculations:
If you do not see the list in my screen shot, it is possible the property type for .TotalExpense is not as it should be. Confirm .TotalExpense is set to Currency (or at least Decimal or Integer so you have mathematical calculations available in the declare expression).