This problem is frustrating me, I am a university student taking a course in introductory linear algebra. This problem is on the list of problems we were supposed to do to get used to the computer system, the problems were supposed to be an easy review. The other 9 problems were very simple but this one has me stumped. 1. The problem statement, all variables and given/known data The course you are taking has 4 tests. The first three tests are for 100 points each and the fourth and final test is for 200 points. You must have an average of at least 80 percent on the 4 tests. On the first three tests you scored 74, 84 and 97. What is the minimum score you need on the fourth test to get an 80 for the course?. 3. The attempt at a solution I think my problem may be with the way I am reading the question?? The way I am interpreting the "points" given for each test. I am interpreting the points as 100 or 200 points out of a total 500, so the first three tests count for 20% of the 80 mark each and the last as 40%. Here's what I've come up with: X is my variable, the score on the 4th test. (74*100+84*100+97*100+200X)/500=80 25500+200X=40000 200X=14500 X=72.5 I checked it through my formula and it worked. (74*100+84*100+97*100+72.5*200)/500=80 Then I thought that the points were in there as a red herring and I simply needed to calculate a simple average and came up with 65% but that answer isn't correct either. Any help would be appreciated.