first you want to find the common difference. So just divide 12 by -8, which is -1.5 and then multiply 27 by -1.5, which is -40.5 and continue two more times.
<span>1st day (2/4)
2nd day (3/4)
3rd day (4/4)
4th day 1 1/4 So she has been running for four days. ( I didnt know if you needed miles or not but, here you go ) <3</span>