Question 1171045
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1. (L ∨ B) ⊃ C     
2. (S ∨ D) • L     
3. L             2, Simplification (SIMP)
4. L ∨ B         3, Addition (ADD)
5. C             4,1 Modus Ponens (MP)
 


In words:  
Line 3 says since "(S or D) and L"  is true, then L is true on its own.

Line 4 says since L is true, "L or B" is also true.  Adding B (or any variable) does not affect the truth since we already know L to be true.  ADD is a freebie.

Line 5 applies "L or B" true to the conditional statement to show the truth of C follows.