A college freshman started the year with $4000 in spending money and after three months, she has $2800 left. assume that she will continue to spend her money at this same rate

Let's find out how much she spent every month.

4000 (starting money) - 2800 (remaining money) = 1200 spent over 3 months

1200/3 = 400 per month was spent

So if she continues to spend 400 a month?

How many months are left? 12 (months of the year) - 3 (months she already spent) = 9

So 9 (remaining months) * 400 (amt per month) = 3600 she'll spend at the going rate over 9 months.

But she only has 2800 left.

2800 (remaining) - 3600 (estimated total of spending) = - 800

So she will be 800$ in debt at the end of the year at the current rate.