P: Lee studies.
Q: Lee does well.
R: Logic is interesting.
S: Logic is easy.
5. Lee must have to study in order to do well. That is because study makes logic interesting, and logic must be interesting for it to be easy. Unless it is easy she won't do well.

The conclusion is the first sentence. In the second sentence, which we will symbolize in two parts, we have first a sufficient condition, then a necessary condition.

P->R, S->R, S v ~Q |- Q->P

We do not have the required movement for a hypothetical syllogism.

..P->R
..S->R
..S v ~Q
.~(Q->P)
.....Q
.....~P
~P.........R
.....~S......R
.............S..~Q
..................X

Note that the tree does not have to show all branches as long as one is clearly open (as is the case with "S").