Choy has $25 in his lunch account at school. He spends $3 each day to eat in the cafeteria. What is Choy's lunch account balance after two weeks of buying his lunch in the cafeteria?
Suppose there are 5 school days in 1 week
Then for 2 weeks we have
At $3 for each day this gives a total spent as:
The amount in the account is $25
So the account at the end of this period has 'deposit - expense'.
The negative $5 means that Choy has borrowed
So he is in debt.