SOLUTION: (H ∨ M) ∨ L L ⊃ H H ⊃ (M ⊃ H) ∼(M ⊃ H) /M

1.   (H or M) or L
2.   L -> H
3.   H -> (M -> H)
4.   ~(M -> H)          |  M

5.   ~H                 3,4 Modus Tollens
6.   ~L                 5,2 Modus Tollens
7.   (H or M)           6,1 Disjunctive Syllogism
8.   Therefore M        7,5 Disjunctive Syllogism