1. Abstain from using gets -- it has several flaws in design. Use getline instead. Also, if you are using C++ then it would be better to use C++ streams instead of a mix of both C and C++.
2. Line 219-225. The loop condition is not proper. You require the stack to be empty to enter the loop and yet you pop items from the stack inside the loop, even though it is empty?
3. I would suggest you to include more comments in your file in the future.
4. You really shouldn't be using strtok(). The assignment requires you to use it? I'm surprised.
5. In standard C++ the header file should be <iostream> not <iostream.h>.
6. Rather than using fixed length C Strings, use the std::string class from <string>. It, at least, is easier to use.
7. Use switch cases wherever you can, instead of using a long if... else if... branch.
8. Organise the implementations of Stack in different headers and source files. E.g., Stack.h, Stack.c.
Finally, a post script:
In deciphering expressions I would suggest you first learn a bit about BNF. It will be of immense help to you if you wish to tokenize and handle such expressions in an easier way.
I have a problem in that the solution >> can enter without equivalent arcs and I want to enter the equation with arcs .. And that the figures in the equation introduced from one status, such as 2. 3. 5, and I want it from one or more status such as 2. 45. 66. 676