何番目？

Say, you and your friend go to see a movie in a theater. You take seats side by side near the end of the rows. When you are waiting for the movie to begin, your friend finds his son sitting on a seat in the front row. Your friend says "Oh, what a coincidence. Look, my son! There, sitting in the front row." You don't know his son. So you want to know where he is sitting and you may want to ask your friend
"通路から何番目の座席？"
But you can't ask him because there is no such word as 何番目 in English. You can only ask "which one?" He may say "The third one from the isle". But you can't ask 何番目.
I had always wanted to know how to ask 何番目. At last I asked it to the same guy who I asked about the times tables, about which I wrote yesterday. Unexpectedly I found it hard to make him understand my question. I told him above mentioned example without using 何番目 and he finally understood what I was asking. He said, a bit abashed, English is not a mathematical language.
I asked. "Isn't it inconvenient if you want to ask a question to draw from him the answer that March is the third month of the year?"
"hmmm.....Good question... How about.... In what numerical order, does March come in the year?.... or How many months are there before March?.... Well, you are the first Japanese, making such a mean question. But interesting. I've got more interested in Japanese."
I guess reverse is also true. There must be a lot of things that English cover but Japanese doesn't. I am also more interested in languages.