Sentence:  Let ‘F' stand for the state of affairs that consists in finite persons possessing and exercising free will. Let ‘p' stand for ‘God exists'; ‘q' for ‘F obtains'; ‘r' for ‘F poses a serious risk of evil'; and ‘s' for ‘There is no option available to God that counters F.' With this in place, the argument may be formalized as follows:/ (1) [(p & q) & r] → s Premiss/ (2) ~s        Premiss/ (3) ~[(p & q) & r]   1, 2 MT/ (4) ~(p & q) v ~r 3 DM/ (5) r         Premiss/ (6) ~(p & q)      4, 5 DS/ (7) ~p v ~q      6 DM/ (3) follows from the conjunction of (1) and (2) by "modus tollens"; <WSD>De Morgan's law</WSD><!-- unemboldened in source --> applied to (3) yields (4); (4) and (5) together lead to (6) by disjunctive syllogism; and another application of <WSD>De Morgan's law</WSD><!-- unemboldened in source --> takes us from (6) to the final conclusion, according to which either God exists or there is free will (but not both). 
Meaning of the word marked with <WSD> tags:  The (negation) of a (conjunction) is the (disjunction) of the negations; expressed in propositional logic as: ¬ (𝑝 ∧ 𝑞) ⇔ (¬ 𝑝) ∨ (¬ 𝑞)