Problems 1, 6 and 7

1 is worth 30pts, 2 to 4 pts off for every mistake

6 is worth 35 pts, 2 to 4 pts off for every mistake

7 is worth 35 pts, and is the only one where many points can be taken off.

use revap def and if axioms, 7pts
use hypoth (equal (app (rev (cdr x))) ...), 7pts
calculate (app nil y), 7pts
use app-assoc, 7pts
use def of rev and if axioms, 7pts