Hahaha, well if I didn't think, then I wouldn't be able to get anything done so my thinking is actually a good thing even if you didn't specifically ask for it. But let's see, x stands for the ions H3O+ and F-. F- is the conjugate base of HF, but I am not sure how knowing the conjugate base would help. I could find Kb through the equation Kw/Ka, but I still don't have x. I feel like I should be able to use the equation Ka = x^2/(y/.250L) and then find x through 10^-2.6 and then solve for y. I don't understand why this shouldn't work. It has all the right variables and I don't see anything missing. I understand that you are trying to drive me towards something to do with the conjugate base, but I am just not sure what exactly that is.