What is the difference between the cost of attending a particular school and the expected family contribution, minus any other financial aid?

Answer 1

Add the financial aid and family contribution. Subtract that sum from the cost of attending a particular school.

Answer 2

And remember that the cost of attending a school/college/university includes the following:

tuition
room and board (apt, food, utilities, etc.)
books, paper, computer, pens, etc.