【Analysis】According to "学+学+学" without carrying over, we can know that "学" has only 3 possibilities.
"学" $=1$, “学习” = 17, “数学” = 51;
"学" $=2$, “学习” $=24$, “数学” $=72$;
"学" $=3$, “学习” $=31$, “数学” $=93$.
The two-digit number represented by "数学" in the vertical calculation has 3 possibilities.
【Solution】Solution: According to the analysis of the problem, we can get:
So the two-digit number represented by "数学" is 51 or 72 or 93, there are a total of 3.
Answer: The two-digit number represented by "数学" in the vertical calculation has 3 possibilities.
Therefore, the answer is: 3.
5. (10 points) In the addition column shown below, the same Chinese characters represent the same digits from 1 to 9, while different Chinese characters represent different digits. The two-digit number represented by "数学" in the column has $\qquad$ possibilities.



The text above is the translation of the provided Chinese text, maintaining the original format and line breaks.