Validity of an argument Can anyone help me solve this question?

Determine whether the following argument is valid. Explain why:

"If Batman were able and willing to prevent corruption, then he would do so. If Batman were unable to prevent
corruption, he would be ineffective; if he were unwilling to prevent corruption, then he would be cruel. Batman
does not prevent corruption. If Batman exists, he is neither ineffective nor cruel. Therefore, Batman does not
exist."
What do you know that you can bring to bear on this question???

It could be that you are being asked to informally assess the argument (in something of the manner suggested in @Lord_Farin's answer). But (since you are asking in a maths forum!), here's how I imagine you are intended to tackle the question:


  The inference here turns on the propositional connectives "if ..then ...", "and", "not" and "or" -- so obvious first step: render the argument into the language of the propositional calculus. 


Do you know how to do that?


  Second step: use the truth-table test to determine whether the formalized argument is valid. 


Do you know how to do that?

If you in principle know how to do both steps, this example is straightforward  and should present no problems (this site isn't for doing all your homework for you! -- but ask again if you got stuck at a particular stage)  If you don't know how to do both steps then you'd better do some background reading and get up to speed!
This argument reminds me of some "proofs" of the non-existence of god. First, you assume that god is good and omnipotent and then notice that despite god being all that there is still evil in the world. Ergo, god doesn´t exist.

The argument is valid, and to see that all you need to know is that P => Q is equivalent to not Q => not P. And that if any proposition is implying a contradiction, then that proposition must be false.

Batman exist. => Batman is not cruel. Batman exists also implies that Batman is not ineffective. Bataman is neither ineffective nor cruel => he prevents corruption. And so Batman exists implies both corruption is prevented AND corruption is not prevented. Therefore that statement must be false.