//set %x What is 2+2? 
//echo -a $remove($wildtok(%x,[*],1,32),[,])
A token is a single "word" that is separated by the token character. Because you have a space as the separator (32), you can't use wildtok with the answer having spaces in it. You must also put a space before the [ as shown above and not have the [ touching the ?.
Of course, you could make your trivia script use the same format for questions that most others use...
//set %trivia What is 2+2*4
//echo -a The question is: $gettok(%trivia,1,42) $+ ?
//echo -a The answer is: $gettok(%trivia,2,42)
Just don't include a ? in the question as it will be added automatically. You could make it NOT add the ? automatically, but most scripts add it, so it may be a good idea to stick to a similar method. That way, you can easily accept the questions from other trivia or have users submit trivia using the same format they are used to using with other trivia scripts.
As a note, you can't have a * in the question itself. Most trivia scripts also have a "KAOS" type question, where no hints are given and there are multiple answers that are divided by *'s such as:
//set %trivia What is 2+2*4*Four
People can answer with both answers and get points for both answers. Obviously, you wouldn't want to give points for 4 and four because they are the same thing, but you can do something like that for other questions.