Math Help - Prove validity of an argument by Indirect derivation

1. Prove validity of an argument by Indirect derivation

Establish the validity of this argument by means of an unmixed indirect derivation.

~(P-->Q)-->Q
$\therefore$ P-->Q

Attempt:

1. Show P --> Q
2. ~ (P -->Q) Assumption( Indirect Derivation)
3. ~ (P -->Q) --> Q
4. Q

Remark: I cannot find the contradiction, and am not sure whether line 4 can be used for Indirect Derivation.

2. $\neg \left( {p \to q} \right) \equiv p \wedge \neg q$
Simplification gives $\neg q$.
But $\neg \left( {p \to q} \right) \to q\;\& \,\neg q$ gives $p\to g$.

3. Originally Posted by Plato
$\neg \left( {p \to q} \right) \equiv p \wedge \neg q$
Simplification gives $\neg q$.
But $\neg \left( {p \to q} \right) \to q\;\& \,\neg q$ gives $p\to g$.
I see you did it by Modus tollens.