This is exercise 1, which Ian completed:

This is exercise 2, which Ian was unable to get to work successfully:

Exercise 2 went through a very long revision process, but ultimately I could not get it to recognize the phrase that precedes the numbers needed to compile the average. I understand how to build the average once its components are assembled, but I’m not sure how to get it to work now. Any suggestions on this would be greatly appreciated, because I am thoroughly stumped.

This is exercise 3, which Natalia completed:

And this is exercise 4, which Natalia also completed: