This is partly a test of your understanding of personal budgeting, more so that than a math problem. Your answer might be different from your friend's, yet be acceptable.
Todd's net monthly income: $2,000
Todd's monthly expenses:
Rent: $300
Utilities 50
Books/supplies 250
Food and meals
Transportation
Incidentals
Clothing
Entertainment
Total $
Add up the given costs ($300, $50 and $250). Subtract the sum from $2000. What's left you could label "Miscellaneous expenditures." Then your budget would look like this:
Todd's monthly expenses:
Rent: $300
Utilities 50
Books/supplies 250
Miscellaneous x
Note that these four items must add up to $2,000.