created first exercise
WIP, first problem
complete problem 2
problem 3
complete problem 4
complete problem 5
finishes exercise 1
exercise 2 implementation with .reverse method
progress made on each of exercises 1-3, but no solution to 2 or 3.  test for exercise 1 is brittle.
Sketched questions about linked lists
add final question to problem 6
add string solutions
remove X's from problem descriptions:
Starting solution
remove x fro question #2
fix problem 1 with for loop
solved the first problem
WIP, working version for problem_7
finished problem 2
add more tests to problem_7