the magic sums are 15, 34, and42
There is no cheat in any mission in any 39 clues game!
mission 7 39 clues answer for here lies b. fore e . fines
arctic
On a bookshelf at the top
yep
Boxes on Beechey Isle
456
good
there arent any
there is no magic box
Arctic is the code you have to type in.
Near the bookcase on the right.