Acollege 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.

To solve this question, you need to know the rate in which the money is being spent. First, you know the y-intercept, which is 4000, or the money she owned before spending it. Next, you know, how much she had spent in the duration of 3 months.  So, if you substitute those numbers into y=ax+b, it would be 2800=-3a+4000 (or 2800=4000-3a either way it is equivalent) If you solve this, you know that the college freshman is spending her money at a rate of $400 per month. Hope this helps :)

4000-2800=1200

1200/3 equals 400 a moth

If she continues, she will have enough money for 7 more months