Question 707955
You have A (ie you're assuming A is true) and you have this


A -> (J -> L)


So you can use modus ponens to get J -> L


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You have this statement


(J->L)->(M->N)


and you can use modus ponens with this and the "J -> L" you got earlier to get M -> N


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Now you have M -> N and (M->N)->[(J->L)->O]


Use modus ponens to get (J->L)->O


Then use modus ponens again with J -> L and (J->L)->O to get O


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You now have O and O -> (A -> B)


Use modus ponens to get A -> B


Finally, use modus ponens with A and A -> B to get B


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So all of the given statements and using modus ponens a bunch of times leads us to the conclusion of B


This proves that the argument and conclusion is valid.