SOLUTION: premise (P&Q)V(R&S) Premise R->L goal ~P->L

1. (P & Q) V (R & S)
2.  R -> L              / ~P -> L

                    | 3. ~P          assumption for conditional proof
                    | 4. ~P V ~Q     3. addition
                    | 5. ~(P & Q)    4. deMorgan's law
                    | 6. R & S       1,5, disjunctive syllogism
                    | 7. R           6, simplification
                    | 8. L           2,7, modus ponens

8. ~P -> L       lines 3-8 for conditional proof.

Edwin