I teach math in the first year of the university in Argentina, in one of the midterm of linear algebra curses we have a word problem and three dry problems. A few years ago, I added something like (I don't remember the details, so let's made up a new version):

> *John buys a 25' TV and a 30' TV. They usually in total cost $3000. He has a coupon for a 10% discount on the 25' TV and a 20% discount for the 30' TV so he paid $2500. How much does each of the TV cost without coupons?"

I was wondering how many of them would add the 25' and 30' to the matrix and use the Gauss method to solve it, something like:

  25  1  10% | 3000
  30  1  20% | 2500

I was very happy that they were able to ignore the irrelevant size of the TV. I wonder what would happens if it's not a topic that is so usual.