Webwork: Add more exercises to chapter 1

[apurvnakade]

I found a few more webwork exercises for Chapter 1 that were compatible with Pretext.

Exercise 5 https://apurvnakade.github.io/nulib-oer-linear-algebra/s_ge.html#exercise-31

Exercise 6 https://apurvnakade.github.io/nulib-oer-linear-algebra/s_ge.html#exercise-32

Exercise 1 https://apurvnakade.github.io/nulib-oer-linear-algebra/s_solving.html#exercise-38

Exercise 2 https://apurvnakade.github.io/nulib-oer-linear-algebra/s_solving.html#exercise-39