I've never written a bot. I thought perhaps that the process of parsing instructions (we could put more than one variable in the equation), then writing code to solve, might be more effort than it's worth to them. Especially if we're doing something that is somewhat unique so their reward would only be one page. However, phildawes is apparently implying that once the bots have parsed the problem and know what to solve for they could go to a page that implements Mathematica and submit the problem to be solved, therefore saving the time required to write problem-solving code. I didn't realize they worked like that.