One interviewer went to the board and wrote out a math problem, it was quite sloppy and hard to read I was able to him the solution was incorrect but I wasn't able to tell him why. I spent some time to clarify what he had written but we didn't get any closer, it was too hard to read his writing. He had the problem printed on a piece of paper with the answer I guess because he couldn't show me the original. I asked if we could move on and he insisted we resolve the problem. In the end we ran out of time spending well over half the interview on that problem. He said he would email me the problem so I could solve it at home. He never did.