B-12：be off the beam 走歪门邪道
A: Have you worked out the answer to this problem?
A: 这道题目做出来了吗？
B：Not yet. I just can't calculate the result.
B：还没有。我就是算不出结果来。
A: Let me see. Ah, you are off the beam. Look here.
A: 让我看看。啊，你搞错了。看看这儿。
B: Oh, I see.
B：啊，原来如此。
